Counting fatalities of just those on a flight, the deadliest airplane crash in the United States was American Airlines flight 191. On May 25, 1979, the plane crashed near Chicago’s O’Hare International Airport after losing an engine during takeoff. All 271 people on board were killed as well as 2 people not on the flight.
Counting fatalities of both those on the flight and the ground, American Airlines flight 11 and United Airlines flight 175 were the deadliest crashes in the United States. Both planes were hijacked by terrorists on September 11, 2001, and flown into the World Trade Center in New York City. Some 2,750 people died in the two attacks.