 On March 11, 1958 a U.S. Air Force B-47 Stratojet with a nuclear payload left for nuclear training exercises for war preparations in the United Kingdom and South Africa.The navigator mistakenly pulled the emergency release pin which resulted in the bomb falling out of the plane.Although the bomb was not armed with the trigger (a removable capsule of fissionable material which was securely stored in a containment area on board the plane), it nevertheless contained a high-explosive detonator.