Lighter-than-air aircraft with steering and propulsion systems. Airships could be nonrigid (blimps), semirigid, or rigid. They all included a large cigar-shaped bag or balloon filled with a gas such as hydrogen or helium, a car or gondola suspended below the balloon that held the crew and passengers, engines to drive the propellers, and rudders for steering. Attempts to control the flight of balloons began soon after their invention in the 1780s. The first propeller-driven airship, built by Henri Giffard, flew in 1852 in France; design improvements led to construction of the rigid zeppelin (1900). The nonrigid helium-filled blimp was principally developed by Alberto Santos-Dumont (1873–1932). In 1928 Germany began regular transatlantic airship passenger service. Several explosions, particularly the 1937 Hindenburg disaster, and airplane developments made the airship commercially obsolete. See alsoballoon.