A B-52 bomber like this one broke up in mid-air and dropped its payload over Greensboro, N.C., in 1961.
A U.S. nuclear incident worse than those in Hiroshima and Nagasaki was avoided only by luck one night in 1961, as two atomic bombs hit the ground near Goldsboro, N.C., CNN reported.
A B-52 bomber flying over the area had a right wing failure, CNN reported a declassified National Security Archive document as saying. The plane broke apart and its passengers, the two bombs, fell out.
One of the bombs' parachute deployed; the other did not. And the sequence to arm and detonate the bombs began on both. Both bombs hit the ground, but amazingly, didn't go off. Mechanical failures on both bombs kept them from exploding.
If they had detonated, the damage would have killed tens of thousands of people. The bombs' explosive yield was 3.8 megatons. The bombs dropped on Hiroshima and Nagasaki were 0.01 and 0.02 megatons.
While not common, accidents like these do happen at the rate of about one a year -- or at least they did between 1950 and 1980, when there were 32 accidents involving nuclear weapons, according to CNN.
According to CNN's reports, "There are at least 21 declassified accounts between 1950 and 1968 of aircraft-related incidents in which nuclear weapons were lost, accidentally dropped, jettisoned for safety reasons or on board planes that crashed.
"The accidents occurred in various U.S. states, Greenland, Spain, Morocco and England, and over the Pacific and Atlantic oceans and the Mediterranean Sea."
As for the Goldsboro incident, at the time, Secretary of Defense Robert McNamara commented: "By the slightest margin of chance, literally the failure of two wires to cross, a nuclear explosion was averted."