There never has been even a partial, inadvertent U.S. nuclear detonation despite the very severe stresses imposed upon the weapons involved in these accidents. All `detonations' reported in the summaries involved conventional high explosives (HE) only. Only two accidents, those at Palomares and Thule, resulted in a widespread dispersal of nuclear materials.
Nuclear weapons are never carried on training flights. Most of the aircraft accidents represented here occurred during logistic/ferry missions or airborne alert flights by Strategic Air Command (SAC) aircraft. Airborne alert was terminated in 1968 because of: Accidents, particularly those at Palomares and Thule.
The rising cost of maintaining a portion of the SAC bomber force constantly on airborne alert, and, The advent of a responsive and survivable intercontinental ballistic missile force which relieved the manned bomber force of a part of its more time-sensitive responsibilities. (A portion of the SAC force remained on nuclear ground alert).
Although normal DOD policy is to neither confirm nor deny the presence of nuclear weapons or components, recently revised DOD Directive 5230.16 governing public affairs guidance allows for confirmation when required to protect public safety or as a means of reducing widespread public alarm. Therefore, in some of the events summarized here, confirmation of presence is not published. Except for Palomares and Thule, it is not possible to specify the location of the accidents that occurred overseas.
December 8, 1964/B-58/Bunker Hill (Now Grissom) AFB, Indiana: SAC aircraft were taxiing during an exercise alert. As one B-58 reached a position directly behind the aircraft on the runway ahead of it, the aircraft ahead brought advanced power. As a result of the combination of the jet blast from the aircraft ahead, the icy runway surface conditions, and the power applied to the aircraft while attempting to turn onto the runway, control was lost and the aircraft slid off the left hand side of the taxiway. The left main landing gear passed over a flush mounted taxiway light fixture and 10 feet farther along in its travel, grazed the left edge of a concrete light base. Ten feet farther, the left main landing gear struck a concrete electrical manhole box, and the aircraft caught on fire. When the aircraft came to rest, all three crew members aboard began abandoning the aircraft. The aircraft commander and defensive systems operator egressed with minor injuries. The navigator ejected in his escape capsule, which impacted 548 feet from the aircraft. He did not survive. Portions of the five nuclear weapons on board burned; contamination was limited to the immediate area of the crash and was subsequently removed.