The promise of the Hindenburg, a hydrogen-filled airship that could cross the Atlantic in half the time of a ship at sea, exploded along with the craft itself as it prepared to land in Lakehurst, New Jersey in May 1937. Of the 100 people on board that day, 35 died.
Scientists have debated the reason for the explosion for decades. They knew that a spark ignited leaking hydrogen, but they differed on the reason for the spark and the leaking gas. Theories included lightning, explosive properties in paint, and a bomb.
However, in 2013, a team of experts ruled out the other theories and determined that the Hindenburg had become charged with static electricity from a thunderstorm. Either a faulty gas valve or broken wire caused hydrogen to leak into the ventilation shafts. A spark of static electricity ignited the hydrogen, which started the fire in the tail section and led to the explosion.
"I think the most likely mechanism for providing the spark is electrostatic," said British aeronautical engineer Jem Stansfield. "That starts at the top, then the flames from our experiments [blowing up or setting fire to scale models of the airship] would've probably tracked down to the center. With an explosive mixture of gas, that gave the whoomph when it got to the bottom."