As August 1921 ended, the smoldering remains of the ZR-2, the world’s largest dirigible, were visible above England’s Humber Estuary.

On its last test flight before being turned over to the U.S. Navy for a transatlantic flight to Lakehurst, N.J. with a crew of 49 men including 17 Americans, it broke in half and its hydrogen gas was ignited. As a crowd watched from the ground, all but five crew members were killed.

The crash would set off wild speculation and finger-pointing and threatened to put an end to America’s Lighter Than Air…