Fifty-seven years ago today, on Jan. 28, 1968 (Dec. 29, 1967), an American plane carrying a hydrogen bomb crashed into Greenland. On Jan. 28, 1968, a United States Air Force B-52 bomber carrying four hydrogen bombs crashed into the ice outside Greenland while attempting an emergency landing. According to the Defense Department, the hydrogen bombs "do not self-detonate, so there is no risk of a nuclear explosion in the crash zone." The area is close to the American base in Thule. It is unclear what happened to the hydrogen bombs on board after the plane crashed - whether they were scattered across the ice or sank with parts of the bomber's body through the ice to a depth of 800 feet. One pilot, the co-pilot, died, the Pentagon said, but six other pilots had survived by parachuting safely from the burning aircraft, which at one point tried to make an emergency landing at Thule after the cockpit caught fire. The B-52 bomber, which took off from Plattsburgh Air Force Base in New York, is under the command of Strategic Air Command on an aerial alert mission to protect its bombers from sudden missile attacks. In such missions, each B-52 aircraft usually carries four hydrogen bombs, which are subject to a series of control steps by the flight crew before detonating.