When the US Air Force nearly nuked North Carolina.

This happened in 1961, according to a long-secret document published today:

[T]wo Mark 39 hydrogen bombs... fell to earth after a B-52 bomber broke up in mid-air, and one of the devices behaved precisely as a nuclear weapon was designed to behave in warfare: its parachute opened, its trigger mechanisms engaged, and only one low-voltage switch prevented untold carnage.

Each bomb carried a payload of 4 megatons – the equivalent of 4 million tons of TNT explosive. Had the device detonated, lethal fallout could have been deposited over Washington, Baltimore, Philadelphia and as far north as New York city – putting millions of lives at risk.

I'd never heard about that incident until just now. That happened when I was 10, and I lived in northern Delaware, within that fallout zone.