It was a Cold War era B-52 Stratofortress bomber and Boeing KC-135 Stratotanker mid air collision that destroyed both aircraft and almost caused a nuclear accident. It happened when a B-52G bomber of the USAF Strategic Air Command collided with a KC-135 tanker during mid-air refuelling operation at 31,000 feet (9,450 m) over the Mediterranean Sea, off the coast of Spain. The tanker's flue ignited in the crash, blowing it up, while the bomber broke in to 3 sections before hitting the sea.