A hydrogen bomb that went missing for three months in the Mediterranean Sea is back in the hands of the U.S. military after being found the previous day. The bomb had been lost in January when two U.S. military planes, a KC-135 tanker and a B-52 carrying four thermonuclear weapons, collided during midair refueling. Three of the four bombs fell to the ground near Palomares, Spain. While none of them detonated with a nuclear explosion, the high-explosive triggers in two of the bombs went off upon impact and contaminated the area with radioactive material. A fourth bomb plunged into the water off Spain's southeastern coastline. Following the incident, the Spanish government announced it would no longer allow U.S. planes carrying nuclear weapons to fly over its territory. On March 17, the U.S. Navy, using a midget submarine called the Alvin [found] the bomb 2,500 feet underwater, intact and with its parachute still attached.