page_title: 1968 Thule Air Base B-52 crash
section_title: Thule Monitor Mission
hierarchical_section_title: 1968 Thule Air Base B-52 crash / Thule Monitor Mission
caption_attribution_description: English: Relief location map of Greenland. Projection: EquiDistantConicProjection. Area of interest: N: 85.0° N S: 59.0° N W: -75.0° E E: -10.0° E Projection center: NS: 72.0° N WE: -42.5° E Standard parallels: 1: 64.0° N 2: 80.0° N GMT projection: -JD-42.5/72/64/80/20c GMT region: -R-60.16/57.61/24.5/79.91r GMT region for grdcut: -R-120.24/57.61/24.5/85.78r Relief: SRTM30plus. Made with Natural Earth. Free vector and raster map data @ naturalearthdata.com.
context_page_description: On 21 January 1968, an aircraft accident involving a United States Air Force B-52 bomber occurred near Thule Air Base in the Danish territory of Greenland. The aircraft was carrying four B28FI thermonuclear bombs on a Cold War "Chrome Dome" alert mission over Baffin Bay when a cabin fire forced the crew to abandon the aircraft before they could carry out an emergency landing at Thule Air Base. Six crew members ejected safely, but one who did not have an ejection seat was killed while trying to bail out. The bomber crashed onto sea ice in North Star Bay, Greenland, causing the conventional explosives aboard to detonate and the nuclear payload to rupture and disperse, which resulted in radioactive contamination.
  The United States and Denmark launched an intensive clean-up and recovery operation, but the secondary stage of one of the nuclear weapons could not be accounted for after the operation was completed. USAF Strategic Air Command "Chrome Dome" operations were discontinued immediately after the accident, which highlighted the safety and political risks of the missions. Safety procedures were reviewed and more stable explosives were developed for use in nuclear weapons.
context_section_description: In 1960, the USAF Strategic Air Command (SAC) began Operation Chrome Dome, a Cold War airborne alert program devised by General Thomas S. Power to fly nuclear-armed Boeing B-52 Stratofortress bombers to the borders of the Soviet Union. The flights were scheduled to ensure that twelve bombers were aloft at all times. These bombers gave SAC offensive capability in the event of a Soviet first strike, and provided a significant Cold War nuclear deterrent. Beginning in 1961, B-52 bombers also secretly flew as part of the "Hard Head" mission (or "Thule Monitor Missions") over Thule Air Base. The objective of "Hard Head" was to maintain constant visual surveillance of the base's strategically important Ballistic Missile Early Warning System (BMEWS), which provided early warning of Soviet missile launches. If the communication link between North American Aerospace Defense Command and the base was severed, the aircraft crew could determine if the interruption resulted from an attack or a technical failure. The monitoring mission started when the designated aircraft reached a waypoint at 75°0′N 67°30′W in Baffin Bay and entered a figure-eight holding pattern above the air base at an altitude of 35,000 feet (11,000 m).
  In 1966, United States Secretary of Defense Robert McNamara proposed cutting "Chrome Dome" flights because the BMEWS system was fully operational, the bombers had been made redundant by missiles, and $123 million ($969 million as of 2020) could be saved. SAC and the Joint Chiefs of Staff opposed the plan, so a compromise was reached whereby a smaller force of four bombers would be on alert each day. Despite the reduced program and the risks highlighted by the 1966 Palomares B-52 crash, SAC continued to dedicate one of the aircraft to monitoring Thule Air Base. This assignment was without the knowledge of civilian authorities in the United States, who SAC determined did not have the "need to know" about specific operational points.
caption: Greenland
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