Just eight years after losing a nuclear bomb off Georgia, the US Air Force lost four more nuclear weapons. This time the loss took place over Palomares in Spain. On January 17, 1966, a B-52 collided with a KC-135 tanker plane during a midair refuelling. Seven of the 11 crewmen aboard the two aircraft were killed. It would take the air force about 80 days before the elusive weapons were finally found, three on land, the fourth in the Mediterranean Sea. According to the Washington DC-based Brookings Institution, the costs of the recovery effort and settlement claims came to more than US$180 million. According to the environmental group Greenpeace, there may be as many as 50 nuclear warheads in the world's oceans - most from the former Soviet Union.