Palomares Incident, January 17, 1966
A U.S. B52 bomber collided with KC-135 tanker during mid-air flight refuelling over the coast of Spain. The tanker was completely destroyed in the incident, while the B52 broke apart, spilling four hydrogen bombs from its broken fuselage. The non-nuclear weapons in two of the bombs detonated on impact with the ground, contaminating of a 490 acre area with radioactive plutonium. One of the devices was recovered from the Mediterranean Sea.

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