On January 24, 1961, a U. S. Air Force B-52 Stratofortress carrying two 3.
8-megaton Mark 39 thermonuclear bombs suffered a major fuel leak in its right wing while flying over Goldsboro, North Carolina. As the crew attempted an emergency landing, the wing broke apart, causing the aircraft to break up mid-air. The catastrophic breakup released both nuclear weapons into freefall from an altitude of nearly 10,000 feet.
Each bomb possessed explosive power roughly 250 times greater than the device detonated over Hiroshima. As the bombs fell, their automated safety mechanisms began to activate as if they had been intentionally dropped in a combat strike. On one of the weapons, the lanyard was pulled, opening its parachutes and triggering five of its six internal arming devices.
It went through its full sequence: charging the firing capacitors, deploying the drogue chute, and switching to battery power. When the bomb landed intact in a tree near Faro, North Carolina, only one simple low-voltage safety switch had prevented a full thermonuclear detonation that would have devastated a massive portion of the East Coast. The second bomb fell into a muddy field at high speed, breaking apart upon impact; its high-explosive conventional charges did not detonate, but its secondary nuclear core sank deep into the wetland mud and was never fully recovered.
Declassified documents released in 2013 revealed how terrifyingly close the United States came to accidentally nuking its own territory due to failing fail-safes.