On March 11, 1958, an Air Force B-47 Stratojet was making its way to the United Kingdom from the Hunter Air Force Base in Savannah, Georgia. It was sent out to help, in Operation Snow Flurry, but it never made it.
As the plane was cruising over South Carolina, the pilots noticed that a fault light in the cockpit was indicating a problem with the locking pin on the bomb harnesses in the cargo bay. You see, back then, the plane was required to carry nuclear weapons at all times just in case a war broke out with the Soviet Union. The nuclear bomb in question was as 26-kiloton Mark 6, even more, powerful than the Fat Man bomb dropped on Nagasaki.
Air Force Captain Bruce Kulka was acting as the navigator on the flight and decided to go back and check out the problem. While pulling himself up from the plane floor, he reached around the bomb to steady himself but ended up grabbing the bomb's emergency release pin instead. Kulka could only look on in horror as the bomb dropped to the floor, pushed open the bomb bay doors, and fell 15,000 feet toward rural South Carolina.
Fortunately for the entire East Coast, the bomb's fission core was stored in a separate part of the plane, meaning that it wasn't technically armed. Unfortunately for Walter Gregg, it was still loaded with about 7,600 pounds of traditional explosives. The resulting explosion leveled his house, flattened a good section of the forest, and created a mushroom cloud that could be seen for miles. When the dust had settled, the bomb had caused a 25-foot-deep crater that measured 75 feet wide, and while it had injured a number of Gregg's family members, miraculously, not a single person was killed.