http://www.history.com/this-day-in-history/h-bomb-lost-in-spain

1966
H-bomb lost in Spain


On this day, a B-52 bomber collides with a KC-135 jet tanker over Spain’s Mediterranean coast, dropping three 70-kiloton hydrogen bombs near the town of Palomares and one in the sea. It was not the first or last accident involving American nuclear bombs.

As a means of maintaining first-strike capability during the Cold War, U.S. bombers laden with nuclear weapons circled the earth ceaselessly for decades. In a military operation of this magnitude, it was inevitable that accidents would occur. The Pentagon admits to more than three-dozen accidents in which bombers either crashed or caught fire on the runway, resulting in nuclear contamination from a damaged or destroyed bomb and/or the loss of a nuclear weapon. One of the only “Broken Arrows” to receive widespread publicity occurred on January 17, 1966, when a B-52 bomber crashed into a KC-135 jet tanker over Spain.

The bomber was returning to its North Carolina base following a routine airborne alert mission along the southern route of the Strategic Air Command when it attempted to refuel with a jet tanker. The B-52 collided with the fueling boom of the tanker, ripping the bomber open and igniting the fuel. The KC-135 exploded, killing all four of its crew members, but four members of the seven-man B-52 crew managed to parachute to safety. None of the bombs were armed, but explosive material in two of the bombs that fell to earth exploded upon impact, forming craters and scattering radioactive plutonium over the fields of Palomares. A third bomb landed in a dry riverbed and was recovered relatively intact. The fourth bomb fell into the sea at an unknown location.

http://www.roadsideamerica.com/story/24951