In February 1950 a Convair B-36B bomber jettisoned the nuclear weapon it was carrying when the planes engines caught on fire. This was the first lost nuke incident in history.
The bomber was engaged in a practice run at the time which was to include a simulated attack upon San Francisco. “Hey, let’s pretend we’re nuking San Francisco, that’ll be fun!”
The plane was abandoned in flight by the crew and the bomb was ejected by the crew and detonated in the air, resulting in a large conventional explosion. Five of the 17 crew members died in the accident. The plane crashed in Northern British Columbia.