Returning one of several US Mark 4 nuclear bombs secretly deployed at Goose Bay AFB in Labrador, a USAF Boeing B-50 Superfortress had engine trouble and jettisoned the weapon at 10,500 feet (3,200 m).

[1] The non-nuclear explosion shook area residents and scattered nearly 100 pounds (45 kg) of radioactive uranium (U-238) used in the weapon's tamper.

The plutonium core ("pit"), which is the key component for a nuclear reaction and detonation, was not installed in the bomb at the time.

Per standard protocol, the plutonium trigger was always removed prior to flight and shipped separately to prevent accidental nuclear activation.

[2] The incident was immediately covered up at the time, and explained away as 500-pound (230 kg) military practice bombs being detonated.