1961 Goldsboro B-52 crash - Wikipedia, the free encyclopedia

▻http://en.wikipedia.org/wiki/1961_Goldsboro_B-52_crash

Five of the six arming mechanisms on one of the bombs activated, causing it to execute many of the steps needed to arm itself, such as charging the firing capacitors and, critically, deployment of a 100-foot-diameter (30 m) retard parachute. The parachute allowed that bomb to hit the ground with little damage.
According to former military analyst Daniel Ellsberg, he saw highly classified documents indicating that the pilot’s safe/arm switch was the only one of the six arming devices on the bomb that prevented detonation. The Pentagon claims that there was no chance of an explosion and that two arming mechanisms had not activated. A United States Department of Defense spokesperson told United Press International reporter Donald May that the bomb was unarmed and could not explode. Later, however, it was found that both bombs were fully functional and that a single low-voltage switch was indeed all that prevented detonation.

Et quelques années plus tard (1966) la bombe perdue de Palomares…

Accident nucléaire de Palomares - Wikipédia
▻http://fr.wikipedia.org/wiki/Accident_nucl%C3%A9aire_de_Palomares

Des quatre bombes H de type Mk 28 que le B-52G transportait, trois sont retrouvées à terre près du village de Palomares en Andalousie. Deux sont détruites à l’impact au sol. Les explosifs conventionnels de deux bombes explosent, dispersant environ 4,5 kg de plutonium sur 250 hectares jusqu’aux fermes situées à 1,6 km des côtes. La troisième bombe touche le sol et reste presque intacte près de Palomares. La quatrième bombe est perdue au large des côtes : tombée dans la mer Méditerranée, elle est récupérée intacte après deux mois et demi de recherches.