 On January 17, 1966, a 1.45-megaton-of-TNT equivalent thermonuclear bomb (Teller–Ulam design) was lost in the Mediterranean Sea during a United States Air Force collision over Palomares, Spain.Seven crew members were killed in the mid-air crash of a B-52 bomber and a KC-135 refueling plane.The crash dropped three thermonuclear bombs on the land, and one in the sea.