{
  "proofs_version": 1,
  "manifest_id": "manifest-history-of-the-b-52-bomber-merged-2338081b",
  "sentence_count": 50,
  "classes": {
    "grounded": 43,
    "verbatim": 1,
    "attributed": 6
  },
  "proofs": [
    {
      "section_id": "introduction",
      "sentence": "Air Force service in 1955 and has remained operational ever since.[^src-b-52-bomber-invented-1c5fa0a0]",
      "source_ids": [
        "src-b-52-bomber-invented-1c5fa0a0"
      ],
      "entailment_class": "grounded",
      "specifics": [
        {
          "kind": "year",
          "value": "1955",
          "found_in": [
            "src-b-52-bomber-invented-1c5fa0a0"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "Air Force",
          "found_in": [
            "src-b-52-bomber-invented-1c5fa0a0"
          ],
          "via": "evidence"
        }
      ],
      "quote": "When the B-52 entered U.S. Air Force(USAF) service in 1955, it began a career that continued into the twenty-first century.",
      "quote_source": "src-b-52-bomber-invented-1c5fa0a0"
    },
    {
      "section_id": "introduction",
      "sentence": "Military officials believe the fleet can continue through the century mark with regular modifications and modernization.[^src-what-does-the-future-hold-for--cb9701a8]",
      "source_ids": [
        "src-what-does-the-future-hold-for--cb9701a8"
      ],
      "entailment_class": "verbatim",
      "specifics": [],
      "verbatim_source": "src-what-does-the-future-hold-for--cb9701a8",
      "verbatim_span": [
        203,
        323
      ],
      "quote": "military officials believe the fleet can continue through the century mark with regular modifications and modernization.",
      "quote_source": "src-what-does-the-future-hold-for--cb9701a8"
    },
    {
      "section_id": "introduction",
      "sentence": "Boeing's own announcement of a $2 billion contract for the B-52 Commercial Engine Replacement Program frames the platform as the \"crucial backbone of the United States' nuclear triad,\" with new Rolls-Royce F-130 engines intended to keep it relevant into 2050 and beyond.[^src-boeing-wins-2b-award-to-modern-a11e372f]",
      "source_ids": [
        "src-boeing-wins-2b-award-to-modern-a11e372f"
      ],
      "entailment_class": "grounded",
      "specifics": [
        {
          "kind": "year",
          "value": "2050",
          "found_in": [
            "src-boeing-wins-2b-award-to-modern-a11e372f"
          ],
          "via": "evidence"
        },
        {
          "kind": "money",
          "value": "$2 billion",
          "found_in": [
            "src-boeing-wins-2b-award-to-modern-a11e372f"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "B-52 Commercial Engine Replacement Program",
          "found_in": [
            "src-boeing-wins-2b-award-to-modern-a11e372f"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "United States",
          "found_in": [
            "src-boeing-wins-2b-award-to-modern-a11e372f"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "Rolls-Royce F-130",
          "found_in": [
            "src-boeing-wins-2b-award-to-modern-a11e372f"
          ],
          "via": "evidence"
        }
      ],
      "quote": "Boeing has been awarded a $2 billion contract from the U.S. Air Force to continue development of the B-52 Commercial Engine Replacement Program.",
      "quote_source": "src-boeing-wins-2b-award-to-modern-a11e372f"
    },
    {
      "section_id": "introduction",
      "sentence": "Design work began in 1946 as the Boeing Model 464.[^src-b-52-bomber-invented-1c5fa0a0]",
      "source_ids": [
        "src-b-52-bomber-invented-1c5fa0a0"
      ],
      "entailment_class": "grounded",
      "specifics": [
        {
          "kind": "year",
          "value": "1946",
          "found_in": [
            "src-b-52-bomber-invented-1c5fa0a0"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "Boeing Model",
          "found_in": [
            "src-b-52-bomber-invented-1c5fa0a0"
          ],
          "via": "evidence"
        }
      ],
      "quote": "The design of the eight-engine turbojet plane that would become the B-52, the Boeing Model 464, began in 1946.",
      "quote_source": "src-b-52-bomber-invented-1c5fa0a0"
    },
    {
      "section_id": "introduction",
      "sentence": "Boeing won the initial contract in June 1946, and the aircraft evolved from a straight-wing turboprop configuration to a final prototype with eight turbojet engines and swept wings.[^src-boeing-b-52-stratofortress-2666c79a]",
      "source_ids": [
        "src-boeing-b-52-stratofortress-2666c79a"
      ],
      "entailment_class": "grounded",
      "specifics": [
        {
          "kind": "year",
          "value": "1946",
          "found_in": [
            "src-boeing-b-52-stratofortress-2666c79a"
          ],
          "via": "evidence"
        }
      ],
      "quote": "After Boeing won the initial contract in June 1946, the aircraft's design evolved from a straight-wing aircraft powered by six turboprop engines to the final prototype YB-52 with eight turbojet engines and swept wings.",
      "quote_source": "src-boeing-b-52-stratofortress-2666c79a"
    },
    {
      "section_id": "introduction",
      "sentence": "The YB-52 made its maiden flight on April 15, 1952, with test pilot \"Tex\" Johnston.[^src-boeing-b-52-stratofortress-2666c79a]",
      "source_ids": [
        "src-boeing-b-52-stratofortress-2666c79a"
      ],
      "entailment_class": "grounded",
      "specifics": [
        {
          "kind": "year",
          "value": "1952",
          "found_in": [
            "src-boeing-b-52-stratofortress-2666c79a"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "YB-52",
          "found_in": [
            "src-boeing-b-52-stratofortress-2666c79a"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "Tex",
          "found_in": [
            "src-boeing-b-52-stratofortress-2666c79a"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "Johnston",
          "found_in": [
            "src-boeing-b-52-stratofortress-2666c79a"
          ],
          "via": "evidence"
        }
      ],
      "quote": "After Boeing won the initial contract in June 1946, the aircraft's design evolved from a straight-wing aircraft powered by six turboprop engines to the final prototype YB-52 with eight turbojet engines and swept wings.",
      "quote_source": "src-boeing-b-52-stratofortress-2666c79a"
    },
    {
      "section_id": "introduction",
      "sentence": "The IWM notes that the aircraft has flown in more conflicts than any other aircraft and has served roles ranging from nuclear deterrent to NASA mothership.[^src-iwm-org-uk-history-cold-war-nu-6f7fd465]",
      "source_ids": [
        "src-iwm-org-uk-history-cold-war-nu-6f7fd465"
      ],
      "entailment_class": "grounded",
      "specifics": [
        {
          "kind": "entity",
          "value": "IWM",
          "found_in": [
            "src-iwm-org-uk-history-cold-war-nu-6f7fd465"
          ],
          "via": "attribution"
        },
        {
          "kind": "entity",
          "value": "NASA",
          "found_in": [
            "src-iwm-org-uk-history-cold-war-nu-6f7fd465"
          ],
          "via": "evidence"
        }
      ],
      "quote": "It has flown in more conflicts than any other aircraft and has been used for a greater range of roles, from a nuclear deterrent at the height of Cold War tensions, to a low-level bomber in Vietnam. It's even served as a mothership for NASA's rocket-powered experimental aircraft.",
      "quote_source": "src-iwm-org-uk-history-cold-war-nu-6f7fd465"
    },
    {
      "section_id": "introduction",
      "sentence": "One newspaper account states the B-52 was first flown in 1954, directly contradicting the 1952 date supported by two other sources.[^src-what-does-the-future-hold-for--cb9701a8][^src-boeing-b-52-stratofortress-2666c79a]",
      "source_ids": [
        "src-what-does-the-future-hold-for--cb9701a8",
        "src-boeing-b-52-stratofortress-2666c79a"
      ],
      "entailment_class": "grounded",
      "specifics": [
        {
          "kind": "year",
          "value": "1954",
          "found_in": [
            "src-what-does-the-future-hold-for--cb9701a8"
          ],
          "via": "evidence"
        },
        {
          "kind": "year",
          "value": "1952",
          "found_in": [
            "src-boeing-b-52-stratofortress-2666c79a"
          ],
          "via": "evidence"
        }
      ],
      "quote": "First flown in 1954, the B-52 has played an instrumental role in every U.S. armed conflict for decades. Since then, the heavy bomber has undergone more than half a dozen transformations to align its technology with the military's changing needs",
      "quote_source": "src-what-does-the-future-hold-for--cb9701a8"
    },
    {
      "section_id": "introduction",
      "sentence": "The competing designs evaluated at the January 26, 1950 conference at USAF Headquarters included a rail-launched flying wing from Fairchild, the swept-wing Convair YB-60, a RAND turboprop aircraft, and designs based on the B-47 airframe.[^src-secretprojects-co-uk-threads-h-e482753b]",
      "source_ids": [
        "src-secretprojects-co-uk-threads-h-e482753b"
      ],
      "entailment_class": "grounded",
      "specifics": [
        {
          "kind": "year",
          "value": "1950",
          "found_in": [
            "src-secretprojects-co-uk-threads-h-e482753b"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "USAF Headquarters",
          "found_in": [
            "src-secretprojects-co-uk-threads-h-e482753b"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "Convair YB-60",
          "found_in": [
            "src-secretprojects-co-uk-threads-h-e482753b"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "Fairchild",
          "found_in": [
            "src-secretprojects-co-uk-threads-h-e482753b"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "RAND",
          "found_in": [
            "src-secretprojects-co-uk-threads-h-e482753b"
          ],
          "via": "evidence"
        }
      ],
      "quote": "On January 26, 1950, a conference was held at USAF Headquarters to consider once again the future of the B-52.",
      "quote_source": "src-secretprojects-co-uk-threads-h-e482753b"
    },
    {
      "section_id": "evidence",
      "sentence": "Air Materiel Command issued performance requirements for a new strategic bomber: a cruise speed of 300 miles per hour at 34,000 feet and a combat radius of 5,000 miles.[^src-boeing-b-52-stratofortress-2666c79a]",
      "source_ids": [
        "src-boeing-b-52-stratofortress-2666c79a"
      ],
      "entailment_class": "grounded",
      "specifics": [
        {
          "kind": "entity",
          "value": "Air Materiel Command",
          "found_in": [
            "src-boeing-b-52-stratofortress-2666c79a"
          ],
          "via": "evidence"
        }
      ],
      "quote": "On 23 November 1945, Air Materiel Command (AMC) issued desired performance characteristics for a new strategic bomber... It was required to cruise at 300 miles per hour (260 kn; 480 km/h) at 34,000 feet (10,000 m) with a combat radius of 5,000 miles (4,300 nmi; 8,000 km).",
      "quote_source": "src-boeing-b-52-stratofortress-2666c79a"
    },
    {
      "section_id": "evidence",
      "sentence": "Boeing responded with the Model 464, a straight-wing aircraft powered by six Wright T35 turboprops, which the Air Force declared the competition winner on June 5, 1946.[^src-boeing-b-52-stratofortress-2666c79a][^src-b-52-bomber-invented-1c5fa0a0]",
      "source_ids": [
        "src-boeing-b-52-stratofortress-2666c79a",
        "src-b-52-bomber-invented-1c5fa0a0"
      ],
      "entailment_class": "grounded",
      "specifics": [
        {
          "kind": "year",
          "value": "1946",
          "found_in": [
            "src-boeing-b-52-stratofortress-2666c79a",
            "src-b-52-bomber-invented-1c5fa0a0"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "Wright T35",
          "found_in": [
            "src-boeing-b-52-stratofortress-2666c79a"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "Air Force",
          "found_in": [
            "src-boeing-b-52-stratofortress-2666c79a",
            "src-b-52-bomber-invented-1c5fa0a0"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "Model",
          "found_in": [
            "src-boeing-b-52-stratofortress-2666c79a",
            "src-b-52-bomber-invented-1c5fa0a0"
          ],
          "via": "evidence"
        }
      ],
      "quote": "After Boeing won the initial contract in June 1946, the aircraft's design evolved from a straight-wing aircraft powered by six turboprop engines to the final prototype YB-52 with eight turbojet engines and swept wings.",
      "quote_source": "src-boeing-b-52-stratofortress-2666c79a"
    },
    {
      "section_id": "evidence",
      "sentence": "In early 1948, USAF headquarters directed Boeing to incorporate aerial refueling, both to reduce the aircraft's size and cost and to preserve its intercontinental range.[^src-b-52-bomber-invented-1c5fa0a0]",
      "source_ids": [
        "src-b-52-bomber-invented-1c5fa0a0"
      ],
      "entailment_class": "grounded",
      "specifics": [
        {
          "kind": "year",
          "value": "1948",
          "found_in": [
            "src-b-52-bomber-invented-1c5fa0a0"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "USAF",
          "found_in": [
            "src-b-52-bomber-invented-1c5fa0a0"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "Boeing",
          "found_in": [
            "src-b-52-bomber-invented-1c5fa0a0"
          ],
          "via": "evidence"
        }
      ],
      "quote": "When the B-52 entered U.S. Air Force(USAF) service in 1955, it began a career that continued into the twenty-first century.",
      "quote_source": "src-b-52-bomber-invented-1c5fa0a0"
    },
    {
      "section_id": "evidence",
      "sentence": "Boeing incorporated the Pratt and Whitney J-57 turbojet the following year, giving the Air Force an all-jet intercontinental bomber.[^src-b-52-bomber-invented-1c5fa0a0]",
      "source_ids": [
        "src-b-52-bomber-invented-1c5fa0a0"
      ],
      "entailment_class": "grounded",
      "specifics": [
        {
          "kind": "entity",
          "value": "Whitney J-57",
          "found_in": [
            "src-b-52-bomber-invented-1c5fa0a0"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "Air Force",
          "found_in": [
            "src-b-52-bomber-invented-1c5fa0a0"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "Pratt",
          "found_in": [
            "src-b-52-bomber-invented-1c5fa0a0"
          ],
          "via": "evidence"
        }
      ],
      "quote": "When the B-52 entered U.S. Air Force(USAF) service in 1955, it began a career that continued into the twenty-first century.",
      "quote_source": "src-b-52-bomber-invented-1c5fa0a0"
    },
    {
      "section_id": "evidence",
      "sentence": "The IWM curator Hattie Hearn describes a more compressed version of this transition: on October 21, 1948, Boeing engineers received a weekend to produce a viable design and submitted a 33-page proposal for an all-jet bomber on Monday, with eight turbojet engines in four under-wing pods, the new airframe heavily based on the B-47 Stratojet.[^src-iwm-org-uk-history-cold-war-nu-6f7fd465]",
      "source_ids": [
        "src-iwm-org-uk-history-cold-war-nu-6f7fd465"
      ],
      "entailment_class": "grounded",
      "specifics": [
        {
          "kind": "year",
          "value": "1948",
          "found_in": [
            "src-iwm-org-uk-history-cold-war-nu-6f7fd465"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "IWM",
          "found_in": [
            "src-iwm-org-uk-history-cold-war-nu-6f7fd465"
          ],
          "via": "attribution"
        },
        {
          "kind": "entity",
          "value": "Hattie Hearn",
          "found_in": [
            "src-iwm-org-uk-history-cold-war-nu-6f7fd465"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "B-47 Stratojet",
          "found_in": [
            "src-iwm-org-uk-history-cold-war-nu-6f7fd465"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "Boeing",
          "found_in": [
            "src-iwm-org-uk-history-cold-war-nu-6f7fd465"
          ],
          "via": "evidence"
        }
      ],
      "quote": "For nearly 70 years, the Boeing B-52 Stratofortress has been the backbone of the United States' strategic bomber force.",
      "quote_source": "src-iwm-org-uk-history-cold-war-nu-6f7fd465"
    },
    {
      "section_id": "evidence",
      "sentence": "The IWM account places the decisive design sprint in late October 1948.[^src-iwm-org-uk-history-cold-war-nu-6f7fd465]",
      "source_ids": [
        "src-iwm-org-uk-history-cold-war-nu-6f7fd465"
      ],
      "entailment_class": "grounded",
      "specifics": [
        {
          "kind": "year",
          "value": "1948",
          "found_in": [
            "src-iwm-org-uk-history-cold-war-nu-6f7fd465"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "IWM",
          "found_in": [
            "src-iwm-org-uk-history-cold-war-nu-6f7fd465"
          ],
          "via": "attribution"
        }
      ],
      "quote": "On October 21st 1948, the Boeing engineers were given a weekend to come up with a viable design... On the Monday, Boeing submitted a 33-page proposal for an all-jet bomber. The new airframe was heavily based on the company's B-47 Stratojet. Powering this huge jet were eight turbojet engines housed in four under-wing pods.",
      "quote_source": "src-iwm-org-uk-history-cold-war-nu-6f7fd465"
    },
    {
      "section_id": "evidence",
      "sentence": "A forum post drawing on aviation historical records indicates that a deliberative conference was held at USAF Headquarters on January 26, 1950, to reconsider the program's direction, with the design then under consideration viewed favorably by Strategic Air Command personnel including General Curtis LeMay, yet the meeting adjourned without a firm decision.[^src-secretprojects-co-uk-threads-h-e482753b]",
      "source_ids": [
        "src-secretprojects-co-uk-threads-h-e482753b"
      ],
      "entailment_class": "grounded",
      "specifics": [
        {
          "kind": "year",
          "value": "1950",
          "found_in": [
            "src-secretprojects-co-uk-threads-h-e482753b"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "USAF Headquarters",
          "found_in": [
            "src-secretprojects-co-uk-threads-h-e482753b"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "Strategic Air Command",
          "found_in": [
            "src-secretprojects-co-uk-threads-h-e482753b"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "General Curtis LeMay",
          "found_in": [
            "src-secretprojects-co-uk-threads-h-e482753b"
          ],
          "via": "evidence"
        }
      ],
      "quote": "On January 26, 1950, a conference was held at USAF Headquarters to consider once again the future of the B-52.",
      "quote_source": "src-secretprojects-co-uk-threads-h-e482753b"
    },
    {
      "section_id": "evidence",
      "sentence": "Alternatives included new proposals from Douglas and Republic, a rail-launched flying wing from Fairchild Aircraft Corporation, the swept-wing Convair YB-60, a RAND Corporation turboprop design, and two new designs based on the B-47 airframe.[^src-secretprojects-co-uk-threads-h-e482753b]",
      "source_ids": [
        "src-secretprojects-co-uk-threads-h-e482753b"
      ],
      "entailment_class": "grounded",
      "specifics": [
        {
          "kind": "entity",
          "value": "Fairchild Aircraft Corporation",
          "found_in": [
            "src-secretprojects-co-uk-threads-h-e482753b"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "Convair YB-60",
          "found_in": [
            "src-secretprojects-co-uk-threads-h-e482753b"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "RAND Corporation",
          "found_in": [
            "src-secretprojects-co-uk-threads-h-e482753b"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "Douglas",
          "found_in": [
            "src-secretprojects-co-uk-threads-h-e482753b"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "Republic",
          "found_in": [
            "src-secretprojects-co-uk-threads-h-e482753b"
          ],
          "via": "evidence"
        }
      ],
      "quote": "Alternatives were considered once again, including new proposals from Douglas and Republic",
      "quote_source": "src-secretprojects-co-uk-threads-h-e482753b"
    },
    {
      "section_id": "evidence",
      "sentence": "The swept-wing jet configuration's victory over a competitive field reflects the strength of LeMay's continued advocacy for the design.[^src-secretprojects-co-uk-threads-h-e482753b]",
      "source_ids": [
        "src-secretprojects-co-uk-threads-h-e482753b"
      ],
      "entailment_class": "attributed",
      "specifics": [],
      "quote": "The Model 464-67 was looked upon favorably by SAC personnel, including General LeMay.",
      "quote_source": "src-secretprojects-co-uk-threads-h-e482753b"
    },
    {
      "section_id": "evidence",
      "sentence": "Test pilot \"Tex\" Johnston flew the YB-52 from Boeing Field near Seattle to Larson Air Force Base in a proving flight lasting 2 hours and 21 minutes.[^src-boeing-b-52-stratofortress-2666c79a]",
      "source_ids": [
        "src-boeing-b-52-stratofortress-2666c79a"
      ],
      "entailment_class": "grounded",
      "specifics": [
        {
          "kind": "entity",
          "value": "Boeing Field",
          "found_in": [
            "src-boeing-b-52-stratofortress-2666c79a"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "Larson Air Force Base",
          "found_in": [
            "src-boeing-b-52-stratofortress-2666c79a"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "Tex",
          "found_in": [
            "src-boeing-b-52-stratofortress-2666c79a"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "Johnston",
          "found_in": [
            "src-boeing-b-52-stratofortress-2666c79a"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "YB",
          "found_in": [
            "src-boeing-b-52-stratofortress-2666c79a"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "Seattle",
          "found_in": [
            "src-boeing-b-52-stratofortress-2666c79a"
          ],
          "via": "evidence"
        }
      ],
      "quote": "After Boeing won the initial contract in June 1946, the aircraft's design evolved from a straight-wing aircraft powered by six turboprop engines to the final prototype YB-52 with eight turbojet engines and swept wings.",
      "quote_source": "src-boeing-b-52-stratofortress-2666c79a"
    },
    {
      "section_id": "evidence",
      "sentence": "Johnston's verdict, as Hearn records it: \"not only a good airplane, it is a hell of a good airplane.\"[^src-iwm-org-uk-history-cold-war-nu-6f7fd465] The B-52 entered USAF service in 1955.[^src-b-52-bomber-invented-1c5fa0a0][^src-boeing-b-52-stratofortress-2666c79a]",
      "source_ids": [
        "src-iwm-org-uk-history-cold-war-nu-6f7fd465",
        "src-b-52-bomber-invented-1c5fa0a0",
        "src-boeing-b-52-stratofortress-2666c79a"
      ],
      "entailment_class": "grounded",
      "specifics": [
        {
          "kind": "year",
          "value": "1955",
          "found_in": [
            "src-iwm-org-uk-history-cold-war-nu-6f7fd465",
            "src-b-52-bomber-invented-1c5fa0a0",
            "src-boeing-b-52-stratofortress-2666c79a"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "B-52",
          "found_in": [
            "src-iwm-org-uk-history-cold-war-nu-6f7fd465",
            "src-b-52-bomber-invented-1c5fa0a0",
            "src-boeing-b-52-stratofortress-2666c79a"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "Hearn",
          "found_in": [
            "src-iwm-org-uk-history-cold-war-nu-6f7fd465"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "USAF",
          "found_in": [
            "src-b-52-bomber-invented-1c5fa0a0",
            "src-boeing-b-52-stratofortress-2666c79a"
          ],
          "via": "evidence"
        }
      ],
      "quote": "For nearly 70 years, the Boeing B-52 Stratofortress has been the backbone of the United States' strategic bomber force.",
      "quote_source": "src-iwm-org-uk-history-cold-war-nu-6f7fd465"
    },
    {
      "section_id": "evidence",
      "sentence": "At that moment, the Soviet Union lacked an intercontinental bomber, and the B-52 gave the United States an advantage in strategic nuclear strike capacity, enabling the USAF to strike Soviet targets from continental United States bases.[^src-b-52-bomber-invented-1c5fa0a0]",
      "source_ids": [
        "src-b-52-bomber-invented-1c5fa0a0"
      ],
      "entailment_class": "grounded",
      "specifics": [
        {
          "kind": "entity",
          "value": "Soviet Union",
          "found_in": [
            "src-b-52-bomber-invented-1c5fa0a0"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "United States",
          "found_in": [
            "src-b-52-bomber-invented-1c5fa0a0"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "USAF",
          "found_in": [
            "src-b-52-bomber-invented-1c5fa0a0"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "Soviet",
          "found_in": [
            "src-b-52-bomber-invented-1c5fa0a0"
          ],
          "via": "evidence"
        }
      ],
      "quote": "When the B-52 entered U.S. Air Force(USAF) service in 1955, it began a career that continued into the twenty-first century.",
      "quote_source": "src-b-52-bomber-invented-1c5fa0a0"
    },
    {
      "section_id": "evidence",
      "sentence": "In 1957, the B-52 carried out the first globe-circling nonstop flight by a jet aircraft.[^src-b-52-bomber-invented-1c5fa0a0]",
      "source_ids": [
        "src-b-52-bomber-invented-1c5fa0a0"
      ],
      "entailment_class": "grounded",
      "specifics": [
        {
          "kind": "year",
          "value": "1957",
          "found_in": [
            "src-b-52-bomber-invented-1c5fa0a0"
          ],
          "via": "evidence"
        }
      ],
      "quote": "in 1957, it carried out the first globe-circling nonstop flight by a jet aircraft.",
      "quote_source": "src-b-52-bomber-invented-1c5fa0a0"
    },
    {
      "section_id": "evidence",
      "sentence": "More precisely, from January 16 to 18, 1957, three B-52Bs completed Operation Power Flite, covering 24,325 miles in 45 hours and 19 minutes with several in-flight refuelings.[^src-boeing-b-52-stratofortress-2666c79a]",
      "source_ids": [
        "src-boeing-b-52-stratofortress-2666c79a"
      ],
      "entailment_class": "grounded",
      "specifics": [
        {
          "kind": "year",
          "value": "1957",
          "found_in": [
            "src-boeing-b-52-stratofortress-2666c79a"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "Operation Power Flite",
          "found_in": [
            "src-boeing-b-52-stratofortress-2666c79a"
          ],
          "via": "evidence"
        }
      ]
    },
    {
      "section_id": "evidence",
      "sentence": "On 21 May 1956, a B-52B dropped a Mk-15 nuclear bomb over Bikini Atoll in a test code-named Cherokee, the first air-dropped thermonuclear weapon.[^src-boeing-b-52-stratofortress-2666c79a]",
      "source_ids": [
        "src-boeing-b-52-stratofortress-2666c79a"
      ],
      "entailment_class": "grounded",
      "specifics": [
        {
          "kind": "year",
          "value": "1956",
          "found_in": [
            "src-boeing-b-52-stratofortress-2666c79a"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "Bikini Atoll",
          "found_in": [
            "src-boeing-b-52-stratofortress-2666c79a"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "Cherokee",
          "found_in": [
            "src-boeing-b-52-stratofortress-2666c79a"
          ],
          "via": "evidence"
        }
      ],
      "quote": "On 21 May 1956, a B-52B (52\u201313) dropped a Mk-15 nuclear bomb over the Bikini Atoll in a test code-named Cherokee. It was the first air-dropped thermonuclear weapon.",
      "quote_source": "src-boeing-b-52-stratofortress-2666c79a"
    },
    {
      "section_id": "evidence",
      "sentence": "The Wikipedia article states that 742 aircraft were built plus the original two prototypes.[^src-boeing-b-52-stratofortress-2666c79a]",
      "source_ids": [
        "src-boeing-b-52-stratofortress-2666c79a"
      ],
      "entailment_class": "attributed",
      "specifics": [
        {
          "kind": "entity",
          "value": "Wikipedia",
          "found_in": [
            "src-boeing-b-52-stratofortress-2666c79a"
          ],
          "via": "attribution"
        }
      ]
    },
    {
      "section_id": "evidence",
      "sentence": "The IWM source gives 744 B-52s built between 1955 and 1962, without separating prototypes from production aircraft.[^src-iwm-org-uk-history-cold-war-nu-6f7fd465]",
      "source_ids": [
        "src-iwm-org-uk-history-cold-war-nu-6f7fd465"
      ],
      "entailment_class": "grounded",
      "specifics": [
        {
          "kind": "year",
          "value": "1955",
          "found_in": [
            "src-iwm-org-uk-history-cold-war-nu-6f7fd465"
          ],
          "via": "evidence"
        },
        {
          "kind": "year",
          "value": "1962",
          "found_in": [
            "src-iwm-org-uk-history-cold-war-nu-6f7fd465"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "IWM",
          "found_in": [
            "src-iwm-org-uk-history-cold-war-nu-6f7fd465"
          ],
          "via": "attribution"
        }
      ],
      "quote": "A total of 744 B-52s were built before production ceased in 1962... finishing up with the H-model \u2013 the only variant that is still in service today.",
      "quote_source": "src-iwm-org-uk-history-cold-war-nu-6f7fd465"
    },
    {
      "section_id": "evidence",
      "sentence": "After 1962, the B-52 remained a mainstay of Strategic Air Command for three decades.[^src-b-52-bomber-invented-1c5fa0a0]",
      "source_ids": [
        "src-b-52-bomber-invented-1c5fa0a0"
      ],
      "entailment_class": "grounded",
      "specifics": [
        {
          "kind": "year",
          "value": "1962",
          "found_in": [
            "src-b-52-bomber-invented-1c5fa0a0"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "Strategic Air Command",
          "found_in": [
            "src-b-52-bomber-invented-1c5fa0a0"
          ],
          "via": "evidence"
        }
      ],
      "quote": "Production of the B-52 ceased in 1962, but it remained a mainstay of the Strategic Air Command for the next three decades.",
      "quote_source": "src-b-52-bomber-invented-1c5fa0a0"
    },
    {
      "section_id": "evidence",
      "sentence": "The platform shifted instead toward nuclear cruise missiles and an expanded conventional strike role, reflecting its evolution from a penetrating bomber to a standoff weapons carrier.[^src-boeing-b-52-stratofortress-2666c79a]",
      "source_ids": [
        "src-boeing-b-52-stratofortress-2666c79a"
      ],
      "entailment_class": "attributed",
      "specifics": [],
      "quote": "After Boeing won the initial contract in June 1946, the aircraft's design evolved from a straight-wing aircraft powered by six turboprop engines to the final prototype YB-52 with eight turbojet engines and swept wings.",
      "quote_source": "src-boeing-b-52-stratofortress-2666c79a"
    },
    {
      "section_id": "evidence",
      "sentence": "During Desert Storm, B-52s dropped 27,000 tons of munitions, amounting to 30 percent of overall Gulf War tonnage, maintained an 86 percent mission-capable rate, and suffered no combat losses.[^src-iwm-org-uk-history-cold-war-nu-6f7fd465]",
      "source_ids": [
        "src-iwm-org-uk-history-cold-war-nu-6f7fd465"
      ],
      "entailment_class": "grounded",
      "specifics": [
        {
          "kind": "percent",
          "value": "30 percent",
          "found_in": [
            "src-iwm-org-uk-history-cold-war-nu-6f7fd465"
          ],
          "via": "evidence"
        },
        {
          "kind": "percent",
          "value": "86 percent",
          "found_in": [
            "src-iwm-org-uk-history-cold-war-nu-6f7fd465"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "During Desert Storm",
          "found_in": [
            "src-iwm-org-uk-history-cold-war-nu-6f7fd465"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "Gulf War",
          "found_in": [
            "src-iwm-org-uk-history-cold-war-nu-6f7fd465"
          ],
          "via": "evidence"
        }
      ],
      "quote": "During Desert Storm, Buffs dropped 27,000 tons of munitions, which amounted to 30 percent of the overall Gulf War tonnage... B-52s maintained a mission-capable rate of 86 per cent and suffered no combat losses... Interviews with Iraqi POWs suggested that 24% of them had deserted due to the threat of B-52s.",
      "quote_source": "src-iwm-org-uk-history-cold-war-nu-6f7fd465"
    },
    {
      "section_id": "evidence",
      "sentence": "Interviews with Iraqi prisoners of war suggested that 24 percent had deserted due to the threat of B-52s.[^src-iwm-org-uk-history-cold-war-nu-6f7fd465]",
      "source_ids": [
        "src-iwm-org-uk-history-cold-war-nu-6f7fd465"
      ],
      "entailment_class": "grounded",
      "specifics": [
        {
          "kind": "percent",
          "value": "24 percent",
          "found_in": [
            "src-iwm-org-uk-history-cold-war-nu-6f7fd465"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "Iraqi",
          "found_in": [
            "src-iwm-org-uk-history-cold-war-nu-6f7fd465"
          ],
          "via": "evidence"
        }
      ],
      "quote": "During Desert Storm, Buffs dropped 27,000 tons of munitions, which amounted to 30 percent of the overall Gulf War tonnage... B-52s maintained a mission-capable rate of 86 per cent and suffered no combat losses... Interviews with Iraqi POWs suggested that 24% of them had deserted due to the threat of B-52s.",
      "quote_source": "src-iwm-org-uk-history-cold-war-nu-6f7fd465"
    },
    {
      "section_id": "evidence",
      "sentence": "As of 2024, 76 B-52s remained in service, with 58 in active forces, 18 in reserve forces, and approximately 12 in long-term storage.[^src-boeing-b-52-stratofortress-2666c79a]",
      "source_ids": [
        "src-boeing-b-52-stratofortress-2666c79a"
      ],
      "entailment_class": "grounded",
      "specifics": [
        {
          "kind": "year",
          "value": "2024",
          "found_in": [
            "src-boeing-b-52-stratofortress-2666c79a"
          ],
          "via": "evidence"
        }
      ]
    },
    {
      "section_id": "evidence",
      "sentence": "The B-52H is scheduled for upgrade to the B-52J designation by 2030, with Initial Operational Capability projected for 2033.[^src-boeing-b-52-stratofortress-2666c79a]",
      "source_ids": [
        "src-boeing-b-52-stratofortress-2666c79a"
      ],
      "entailment_class": "grounded",
      "specifics": [
        {
          "kind": "year",
          "value": "2030",
          "found_in": [
            "src-boeing-b-52-stratofortress-2666c79a"
          ],
          "via": "evidence"
        },
        {
          "kind": "year",
          "value": "2033",
          "found_in": [
            "src-boeing-b-52-stratofortress-2666c79a"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "B-52H",
          "found_in": [
            "src-boeing-b-52-stratofortress-2666c79a"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "Initial Operational Capability",
          "found_in": [
            "src-boeing-b-52-stratofortress-2666c79a"
          ],
          "via": "evidence"
        }
      ],
      "quote": "Production ended in 1962 with the B-52H, with 742 aircraft built, plus the original two prototypes.",
      "quote_source": "src-boeing-b-52-stratofortress-2666c79a"
    },
    {
      "section_id": "evidence",
      "sentence": "A new engine overhaul may allow the aircraft to remain in service until at least the 2050s, when its airframes will be approximately 100 years old.[^src-iwm-org-uk-history-cold-war-nu-6f7fd465]",
      "source_ids": [
        "src-iwm-org-uk-history-cold-war-nu-6f7fd465"
      ],
      "entailment_class": "attributed",
      "specifics": [],
      "quote": "For nearly 70 years, the Boeing B-52 Stratofortress has been the backbone of the United States' strategic bomber force.",
      "quote_source": "src-iwm-org-uk-history-cold-war-nu-6f7fd465"
    },
    {
      "section_id": "disagreements",
      "sentence": "Wikipedia gives the figure as 742 aircraft plus the original two prototypes.[^src-boeing-b-52-stratofortress-2666c79a]",
      "source_ids": [
        "src-boeing-b-52-stratofortress-2666c79a"
      ],
      "entailment_class": "attributed",
      "specifics": [],
      "quote": "After Boeing won the initial contract in June 1946, the aircraft's design evolved from a straight-wing aircraft powered by six turboprop engines to the final prototype YB-52 with eight turbojet engines and swept wings.",
      "quote_source": "src-boeing-b-52-stratofortress-2666c79a"
    },
    {
      "section_id": "disagreements",
      "sentence": "The Imperial War Museum gives 744 built before production ceased in 1962.[^src-iwm-org-uk-history-cold-war-nu-6f7fd465]",
      "source_ids": [
        "src-iwm-org-uk-history-cold-war-nu-6f7fd465"
      ],
      "entailment_class": "grounded",
      "specifics": [
        {
          "kind": "year",
          "value": "1962",
          "found_in": [
            "src-iwm-org-uk-history-cold-war-nu-6f7fd465"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "Imperial War Museum",
          "found_in": [
            "src-iwm-org-uk-history-cold-war-nu-6f7fd465"
          ],
          "via": "attribution"
        }
      ],
      "quote": "A total of 744 B-52s were built before production ceased in 1962... finishing up with the H-model \u2013 the only variant that is still in service today.",
      "quote_source": "src-iwm-org-uk-history-cold-war-nu-6f7fd465"
    },
    {
      "section_id": "disagreements",
      "sentence": "The IWM account is specific: Boeing engineers received the Pratt and Whitney J57 turbojet engine data and in-flight refueling technology, spent a weekend in late October 1948 producing a swept-wing all-jet proposal, and submitted it on a Monday.[^src-iwm-org-uk-history-cold-war-nu-6f7fd465]",
      "source_ids": [
        "src-iwm-org-uk-history-cold-war-nu-6f7fd465"
      ],
      "entailment_class": "grounded",
      "specifics": [
        {
          "kind": "year",
          "value": "1948",
          "found_in": [
            "src-iwm-org-uk-history-cold-war-nu-6f7fd465"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "IWM",
          "found_in": [
            "src-iwm-org-uk-history-cold-war-nu-6f7fd465"
          ],
          "via": "attribution"
        },
        {
          "kind": "entity",
          "value": "Whitney J57",
          "found_in": [
            "src-iwm-org-uk-history-cold-war-nu-6f7fd465"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "Boeing",
          "found_in": [
            "src-iwm-org-uk-history-cold-war-nu-6f7fd465"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "Pratt",
          "found_in": [
            "src-iwm-org-uk-history-cold-war-nu-6f7fd465"
          ],
          "via": "evidence"
        }
      ],
      "quote": "For nearly 70 years, the Boeing B-52 Stratofortress has been the backbone of the United States' strategic bomber force.",
      "quote_source": "src-iwm-org-uk-history-cold-war-nu-6f7fd465"
    },
    {
      "section_id": "disagreements",
      "sentence": "The forum record describes a different moment: a formal conference at USAF Headquarters on January 26, 1950, at which the swept-wing Model 464-67 design was weighed against competing proposals from Douglas, Republic, Fairchild, Convair, and RAND, as well as two new designs based on the B-47 airframe.[^src-secretprojects-co-uk-threads-h-e482753b]",
      "source_ids": [
        "src-secretprojects-co-uk-threads-h-e482753b"
      ],
      "entailment_class": "grounded",
      "specifics": [
        {
          "kind": "year",
          "value": "1950",
          "found_in": [
            "src-secretprojects-co-uk-threads-h-e482753b"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "USAF Headquarters",
          "found_in": [
            "src-secretprojects-co-uk-threads-h-e482753b"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "Model",
          "found_in": [
            "src-secretprojects-co-uk-threads-h-e482753b"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "Douglas",
          "found_in": [
            "src-secretprojects-co-uk-threads-h-e482753b"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "Republic",
          "found_in": [
            "src-secretprojects-co-uk-threads-h-e482753b"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "Fairchild",
          "found_in": [
            "src-secretprojects-co-uk-threads-h-e482753b"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "Convair",
          "found_in": [
            "src-secretprojects-co-uk-threads-h-e482753b"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "RAND",
          "found_in": [
            "src-secretprojects-co-uk-threads-h-e482753b"
          ],
          "via": "evidence"
        }
      ],
      "quote": "The Model 464-67 was looked upon favorably by SAC personnel, including General LeMay.",
      "quote_source": "src-secretprojects-co-uk-threads-h-e482753b"
    },
    {
      "section_id": "disagreements",
      "sentence": "General LeMay backed the Boeing design, yet the conference adjourned without a firm decision.[^src-secretprojects-co-uk-threads-h-e482753b]",
      "source_ids": [
        "src-secretprojects-co-uk-threads-h-e482753b"
      ],
      "entailment_class": "grounded",
      "specifics": [
        {
          "kind": "entity",
          "value": "General LeMay",
          "found_in": [
            "src-secretprojects-co-uk-threads-h-e482753b"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "Boeing",
          "found_in": [
            "src-secretprojects-co-uk-threads-h-e482753b"
          ],
          "via": "evidence"
        }
      ],
      "quote": "The Model 464-67 was looked upon favorably by SAC personnel, including General LeMay.",
      "quote_source": "src-secretprojects-co-uk-threads-h-e482753b"
    },
    {
      "section_id": "disagreements",
      "sentence": "Two sources place the YB-52's maiden flight in April 1952, with Wikipedia specifying April 15 and the pilot as \"Tex\" Johnston, flying from Boeing Field to Larson Air Force Base.[^src-boeing-b-52-stratofortress-2666c79a][^src-b-52-bomber-invented-1c5fa0a0]",
      "source_ids": [
        "src-boeing-b-52-stratofortress-2666c79a",
        "src-b-52-bomber-invented-1c5fa0a0"
      ],
      "entailment_class": "grounded",
      "specifics": [
        {
          "kind": "year",
          "value": "1952",
          "found_in": [
            "src-boeing-b-52-stratofortress-2666c79a",
            "src-b-52-bomber-invented-1c5fa0a0"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "Boeing Field",
          "found_in": [
            "src-boeing-b-52-stratofortress-2666c79a"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "Larson Air Force Base",
          "found_in": [
            "src-boeing-b-52-stratofortress-2666c79a"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "YB",
          "found_in": [
            "src-boeing-b-52-stratofortress-2666c79a"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "Wikipedia",
          "found_in": [
            "src-boeing-b-52-stratofortress-2666c79a"
          ],
          "via": "attribution"
        },
        {
          "kind": "entity",
          "value": "Tex",
          "found_in": [
            "src-boeing-b-52-stratofortress-2666c79a"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "Johnston",
          "found_in": [
            "src-boeing-b-52-stratofortress-2666c79a"
          ],
          "via": "evidence"
        }
      ],
      "quote": "After Boeing won the initial contract in June 1946, the aircraft's design evolved from a straight-wing aircraft powered by six turboprop engines to the final prototype YB-52 with eight turbojet engines and swept wings.",
      "quote_source": "src-boeing-b-52-stratofortress-2666c79a"
    },
    {
      "section_id": "disagreements",
      "sentence": "The Los Angeles Times article states flatly that \"the B-52 was first flown in 1954.\"[^src-what-does-the-future-hold-for--cb9701a8] The Times account is a single newspaper source reporting under deadline conditions.",
      "source_ids": [
        "src-what-does-the-future-hold-for--cb9701a8"
      ],
      "entailment_class": "grounded",
      "specifics": [
        {
          "kind": "year",
          "value": "1954",
          "found_in": [
            "src-what-does-the-future-hold-for--cb9701a8"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "Los Angeles Times",
          "found_in": [
            "src-what-does-the-future-hold-for--cb9701a8"
          ],
          "via": "attribution"
        },
        {
          "kind": "entity",
          "value": "Times",
          "found_in": [
            "src-what-does-the-future-hold-for--cb9701a8"
          ],
          "via": "attribution"
        }
      ],
      "quote": "First flown in 1954, the B-52 has played an instrumental role in every U.S. armed conflict for decades. Since then, the heavy bomber has undergone more than half a dozen transformations to align its technology with the military's changing needs",
      "quote_source": "src-what-does-the-future-hold-for--cb9701a8"
    },
    {
      "section_id": "disagreements",
      "sentence": "The Los Angeles Times article reports that aviation experts describe the B-52 as having \"an impressive safety record, with few known incidents and crashes.\"[^src-what-does-the-future-hold-for--cb9701a8] The same article enumerates a 2008 crash in Guam killing six, a 2016 Guam runway overrun, and a crash at Edwards Air Force Base killing eight crew members.[^src-what-does-the-future-hold-for--cb9701a8]",
      "source_ids": [
        "src-what-does-the-future-hold-for--cb9701a8"
      ],
      "entailment_class": "grounded",
      "specifics": [
        {
          "kind": "year",
          "value": "2008",
          "found_in": [
            "src-what-does-the-future-hold-for--cb9701a8"
          ],
          "via": "evidence"
        },
        {
          "kind": "year",
          "value": "2016",
          "found_in": [
            "src-what-does-the-future-hold-for--cb9701a8"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "Los Angeles Times",
          "found_in": [
            "src-what-does-the-future-hold-for--cb9701a8"
          ],
          "via": "attribution"
        },
        {
          "kind": "entity",
          "value": "Edwards Air Force Base",
          "found_in": [
            "src-what-does-the-future-hold-for--cb9701a8"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "Guam",
          "found_in": [
            "src-what-does-the-future-hold-for--cb9701a8"
          ],
          "via": "evidence"
        }
      ],
      "quote": "Now, an inquiry into why a B-52 Stratofortress crashed Monday shortly after takeoff at Edwards Air Force Base, killing eight, is renewing questions about the 70-year-old planes",
      "quote_source": "src-what-does-the-future-hold-for--cb9701a8"
    },
    {
      "section_id": "analysis",
      "sentence": "The corroborated record establishes that production ended in 1962, with 742 aircraft built plus two prototypes, or 744 total depending on accounting convention.[^src-boeing-b-52-stratofortress-2666c79a][^src-iwm-org-uk-history-cold-war-nu-6f7fd465]",
      "source_ids": [
        "src-boeing-b-52-stratofortress-2666c79a",
        "src-iwm-org-uk-history-cold-war-nu-6f7fd465"
      ],
      "entailment_class": "grounded",
      "specifics": [
        {
          "kind": "year",
          "value": "1962",
          "found_in": [
            "src-boeing-b-52-stratofortress-2666c79a",
            "src-iwm-org-uk-history-cold-war-nu-6f7fd465"
          ],
          "via": "evidence"
        }
      ],
      "quote": "Production ended in 1962 with the B-52H, with 742 aircraft built, plus the original two prototypes.",
      "quote_source": "src-boeing-b-52-stratofortress-2666c79a"
    },
    {
      "section_id": "analysis",
      "sentence": "The B-58 Hustler, the B-1 Lancer, and the B-2 Spirit each entered service, and the Wikipedia entry notes that superior performance at high subsonic speeds and relatively low operating costs have kept B-52s flying despite those introductions.[^src-boeing-b-52-stratofortress-2666c79a]",
      "source_ids": [
        "src-boeing-b-52-stratofortress-2666c79a"
      ],
      "entailment_class": "grounded",
      "specifics": [
        {
          "kind": "entity",
          "value": "B-58 Hustler",
          "found_in": [
            "src-boeing-b-52-stratofortress-2666c79a"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "B-1 Lancer",
          "found_in": [
            "src-boeing-b-52-stratofortress-2666c79a"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "B-2 Spirit",
          "found_in": [
            "src-boeing-b-52-stratofortress-2666c79a"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "Wikipedia",
          "found_in": [
            "src-boeing-b-52-stratofortress-2666c79a"
          ],
          "via": "attribution"
        }
      ]
    },
    {
      "section_id": "analysis",
      "sentence": "But the IWM curator's account identifies three structural factors: the adaptability of the original over-engineered design, the cooperation between Boeing and the Air Force for continuous modifications, and crew training protocols.[^src-iwm-org-uk-history-cold-war-nu-6f7fd465]",
      "source_ids": [
        "src-iwm-org-uk-history-cold-war-nu-6f7fd465"
      ],
      "entailment_class": "grounded",
      "specifics": [
        {
          "kind": "entity",
          "value": "Air Force",
          "found_in": [
            "src-iwm-org-uk-history-cold-war-nu-6f7fd465"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "IWM",
          "found_in": [
            "src-iwm-org-uk-history-cold-war-nu-6f7fd465"
          ],
          "via": "attribution"
        },
        {
          "kind": "entity",
          "value": "Boeing",
          "found_in": [
            "src-iwm-org-uk-history-cold-war-nu-6f7fd465"
          ],
          "via": "evidence"
        }
      ],
      "quote": "For nearly 70 years, the Boeing B-52 Stratofortress has been the backbone of the United States' strategic bomber force.",
      "quote_source": "src-iwm-org-uk-history-cold-war-nu-6f7fd465"
    },
    {
      "section_id": "analysis",
      "sentence": "By around 2010, US Strategic Command stopped assigning nuclear gravity bombs to the B-52 because the aircraft is no longer considered survivable enough to penetrate modern air defenses.[^src-boeing-b-52-stratofortress-2666c79a]",
      "source_ids": [
        "src-boeing-b-52-stratofortress-2666c79a"
      ],
      "entailment_class": "grounded",
      "specifics": [
        {
          "kind": "year",
          "value": "2010",
          "found_in": [
            "src-boeing-b-52-stratofortress-2666c79a"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "US Strategic Command",
          "found_in": [
            "src-boeing-b-52-stratofortress-2666c79a"
          ],
          "via": "evidence"
        }
      ],
      "quote": "By around 2010, US Strategic Command stopped assigning B61 and B83 nuclear gravity bombs to B-52, and later listed only the B-2 as tasked with delivering strategic nuclear bombs in budget requests. Nuclear gravity bombs were removed from the B-52's capabilities because it is no longer considered survivable enough to penetrate modern air defenses, instead relying on nuclear cruise missiles and focu",
      "quote_source": "src-boeing-b-52-stratofortress-2666c79a"
    },
    {
      "section_id": "analysis",
      "sentence": "B-52s dropped 27,000 tons of munitions, amounting to 30 percent of overall Gulf War tonnage, maintained an 86 percent mission-capable rate, and suffered no combat losses.[^src-iwm-org-uk-history-cold-war-nu-6f7fd465]",
      "source_ids": [
        "src-iwm-org-uk-history-cold-war-nu-6f7fd465"
      ],
      "entailment_class": "grounded",
      "specifics": [
        {
          "kind": "percent",
          "value": "30 percent",
          "found_in": [
            "src-iwm-org-uk-history-cold-war-nu-6f7fd465"
          ],
          "via": "evidence"
        },
        {
          "kind": "percent",
          "value": "86 percent",
          "found_in": [
            "src-iwm-org-uk-history-cold-war-nu-6f7fd465"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "Gulf War",
          "found_in": [
            "src-iwm-org-uk-history-cold-war-nu-6f7fd465"
          ],
          "via": "evidence"
        }
      ],
      "quote": "During Desert Storm, Buffs dropped 27,000 tons of munitions, which amounted to 30 percent of the overall Gulf War tonnage... B-52s maintained a mission-capable rate of 86 per cent and suffered no combat losses... Interviews with Iraqi POWs suggested that 24% of them had deserted due to the threat of B-52s.",
      "quote_source": "src-iwm-org-uk-history-cold-war-nu-6f7fd465"
    },
    {
      "section_id": "analysis",
      "sentence": "Aviation experts quoted in the Los Angeles Times characterize the B-52's safety record as impressive, with few known incidents and crashes.[^src-what-does-the-future-hold-for--cb9701a8]",
      "source_ids": [
        "src-what-does-the-future-hold-for--cb9701a8"
      ],
      "entailment_class": "attributed",
      "specifics": [
        {
          "kind": "entity",
          "value": "Los Angeles Times",
          "found_in": [
            "src-what-does-the-future-hold-for--cb9701a8"
          ],
          "via": "attribution"
        }
      ]
    },
    {
      "section_id": "analysis",
      "sentence": "The same article documents a 2008 crash in Guam that killed six, a 2016 runway overrun in Guam, and a more recent crash at Edwards Air Force Base that killed eight crew members.[^src-what-does-the-future-hold-for--cb9701a8]",
      "source_ids": [
        "src-what-does-the-future-hold-for--cb9701a8"
      ],
      "entailment_class": "grounded",
      "specifics": [
        {
          "kind": "year",
          "value": "2008",
          "found_in": [
            "src-what-does-the-future-hold-for--cb9701a8"
          ],
          "via": "evidence"
        },
        {
          "kind": "year",
          "value": "2016",
          "found_in": [
            "src-what-does-the-future-hold-for--cb9701a8"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "Edwards Air Force Base",
          "found_in": [
            "src-what-does-the-future-hold-for--cb9701a8"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "Guam",
          "found_in": [
            "src-what-does-the-future-hold-for--cb9701a8"
          ],
          "via": "evidence"
        }
      ],
      "quote": "Now, an inquiry into why a B-52 Stratofortress crashed Monday shortly after takeoff at Edwards Air Force Base, killing eight, is renewing questions about the 70-year-old planes",
      "quote_source": "src-what-does-the-future-hold-for--cb9701a8"
    },
    {
      "section_id": "analysis",
      "sentence": "An aircraft designed in the late 1940s entered service in 1955, absorbed technologies it was not originally built for, fought in conflicts its designers could not have anticipated, and now carries a projected service life extending to the 2050s, when its airframes will be approximately 100 years old.[^src-iwm-org-uk-history-cold-war-nu-6f7fd465]",
      "source_ids": [
        "src-iwm-org-uk-history-cold-war-nu-6f7fd465"
      ],
      "entailment_class": "grounded",
      "specifics": [
        {
          "kind": "year",
          "value": "1955",
          "found_in": [
            "src-iwm-org-uk-history-cold-war-nu-6f7fd465"
          ],
          "via": "evidence"
        }
      ]
    },
    {
      "section_id": "analysis",
      "sentence": "The B-52J modernization program, with engine testing expected to begin in 2027 and initial operational capability projected for 2033, confirms the trajectory.[^src-what-does-the-future-hold-for--cb9701a8][^src-boeing-b-52-stratofortress-2666c79a]",
      "source_ids": [
        "src-what-does-the-future-hold-for--cb9701a8",
        "src-boeing-b-52-stratofortress-2666c79a"
      ],
      "entailment_class": "grounded",
      "specifics": [
        {
          "kind": "year",
          "value": "2027",
          "found_in": [
            "src-what-does-the-future-hold-for--cb9701a8"
          ],
          "via": "evidence"
        },
        {
          "kind": "year",
          "value": "2033",
          "found_in": [
            "src-boeing-b-52-stratofortress-2666c79a"
          ],
          "via": "evidence"
        },
        {
          "kind": "entity",
          "value": "B-52J",
          "found_in": [
            "src-boeing-b-52-stratofortress-2666c79a"
          ],
          "via": "evidence"
        }
      ],
      "quote": "The Air Force is currently working toward the newest version of the bomber, testing a new radar system and working with contractors to update its 1960s-era engines... Testing for the new radar system is already underway, while tests for the plane's new engines are expected to begin in 2027",
      "quote_source": "src-what-does-the-future-hold-for--cb9701a8"
    }
  ]
}