In November 1983 , during the joint Spanish-American military exercise CRISEX 83 , U.S. Air Force B-52 strategic bombers were allowed once again to enter Spanish air space and use the Morón Air Base . All B-52s had been previously banned from entering Spanish air space after the 1966 Palomares B-52 crash on January , 17 , 1966 , near Palomares , when a B-52G ( s/n 58-0256 ) being refueled in midair collided with a KC-135 Stratotanker ( s/n 61-0273 ) . The B-52 was carrying four hydrogen bombs . Two of these disintegrated on impact with the ground , dispersing particles of radioactive plutonium over the landscape . One intact H-bomb landed via parachute in a stream near Palomares . The fourth H-bomb fell via parachute into the Mediterranean Sea , about 20 kilometers ( 12 miles ) off the Spanish coast , and it disappeared into deep water . A search lasting for three months using about 12,000 men ensued to try to find the H-bomb . Despite the use of electronic detection equipment by the U.S. Navy , it was never found this way . The H-bomb was finally located after some Spanish commercial fishermen came forward , after a long delay , to say that they had seen the bomb parachuting into the sea
1966 Palomares B-52 crash
1966 Palomares B-52 crash
Morón Air Base