In the late 1950s , three United planes were lost in mid-air collisions that killed everyone on both aircraft involved . On June 30 , 1956 , Flight 718 collided with a Trans World Airlines Lockheed L-1049 Super Constellation over the Grand Canyon in what was then the world 's deadliest commercial airline disaster . In 1958 , Flight 736 crashed in southern Nevada after colliding with a USAF F-100 Super Sabre fighter jet . And on December 16 , 1960 , Flight 826 hit another TWA Super Constellation over New York City . These accidents helped pave the way for modern Air Traffic Control . Also in 1958 , United received its first Douglas DC-8 , its first jet aircraft
Flight 826
1960 New York mid-air collision
History of United Airlines