The first balloon accident, 1785.

On 15th June, 1785, Pilatre de Rozier and Jules Romain attempted to cros the English Channel in a balloon of de Rozier's design, featuring a hydrogen-filled chamber above a compartment filled with hot air. Unfortunately, about 30 minutes after they took off from Boulogne, the hydrogen in the upper compartment caught fire, almost certainly ignited by a spark of static electricity. The horrified watching crowd saw the balloon and its occupants plummet to earth resulting in de Rozier and Romain becoming ballooning's first fatalities.