Just three days after President John F. Kennedy made his inaugural address, a B-52 bomber flying over Goldsboro, North Carolina, broke apart during a failed mid-air refueling procedure around midnight on January 23, 1961. As the aircraft fell to earth, five men were able to eject and land safely, one ejected and did not survive, and two died as the bomber crashed into an area of tobacco and cotton farmland. But, the danger wasn't over.

The bomber carried two Mark 39 hydrogen bombs, which were 240 times more powerful than the atomic bomb dropped on Hiroshima. As pieces of the aircraft fell, one of the bombs went into full warfare mode: it opened its parachutes and the trigger mechanisms switched on. Fortunately, the bomb came with four safety switches that would keep it from detonating. Unfortunately, three of them had failed, and only one low-voltage switch kept the bomb from unleashing 4 megatons—the equivalent of 4 million tons of TNT—of destruction on American soil. 

Once news got out of the accident, the government was quick to say that no lives were in danger, and kept their side of the story for decades after. But now, thanks to a secret document that has came to light with help from the Freedom of Information Act and investigative journalist Eric Schlosser, a senior engineer at Sandia National Laboratories—which was responisible for the mechanical safety of nuclear weapons—confirms that "one simple, dynamo-technology, low voltage switch stood between the United States and a major catastrophe".

"The US government has consistently tried to withhold information from the American people in order to prevent questions being asked about our nuclear weapons policy," Schlosser said. "We were told there was no possibility of these weapons accidentally detonating, yet here's one that very nearly did."

The document, entitled, "Goldsboro Revisited or: How I learned to Mistrust the H-Bomb" by Parker F. Jones from Sandia, goes on to conclude that the bomb's safety mechanism were not up to standard, and that a tiny jolt in electricity could have shorted that final, fourth switch, which kept the bomb from exploding. Once the bomb hit the ground, a firing signal was being sent to its nuclear core, and that highly-vulnerable switch was all that stood between North Carolina and disaster—and quite a different present we now find ourselves in.

What happened to the other bomb? Its parachute got caught in a nearby tree.

[via The Guardian]