The apparent crash of a Malaysian Airlines jetliner in Ukraine came on the 18th anniversary of another huge aviation disaster: the midair explosion and crash of TWA Flight 800 into the Atlantic Ocean off Long Island. All 230 people on board the Boeing 747-100 were killed in the July 17, 1996, tragedy. Although investigators determined the likely cause was a spark igniting vapors in a fuel tank, many conspiracy theories about Flight 800 have persisted, including claims that it was hit by a missile.