American Airlines Flight 191 was a regularly scheduled passenger flight operated by American Airlines from O'Hare International Airport in Chicago, Illinois, to Los Angeles International Airport in Los Angeles, California. On May 25, 1979, the McDonnell Douglas DC-10-10 operating this flight was taking off from runway 32R when it crashed into the ground. All 258 passengers and 13 crew on board were killed, along with two people on the ground. With 273 fatalities, it is the deadliest aviation accident to have occurred in the United States.

The National Transportation Safety Board (NTSB) found that as the aircraft was beginning its takeoff rotation, engine number one (the left engine) separated from the left wing, flipping over the top of the wing and landing on the runway. As the engine separated from the aircraft, it severed hydraulic fluid lines that lock the wing's leading-edge slats in place and damaged a 3-foot (1 m) section of the left wing's leading edge. Aerodynamic forces acting on the wing resulted in an uncommanded retraction of the outboard slats. As the aircraft began to climb, the damaged left wing – with no engine – produced far less lift (stalled) than the right wing, with its slats still deployed and its engine providing full takeoff thrust. The disrupted and unbalanced aerodynamics of the aircraft caused it to roll abruptly to the left until it was partially inverted, reaching a bank angle of 112 degrees, before crashing in an open field by a trailer park near the end of the runway. The engine separation was attributed to damage to the pylon structure holding the engine to the wing, caused by improper maintenance procedures used at American Airlines.

The aircraft involved was a McDonnell Douglas DC-10-10 registered N110AA. It had been delivered on February 25, 1972, and at the time of the crash, it had logged just under 20,000 hours of flying time over seven years. The jet was powered by three General Electric CF6-6D engines. A review of the aircraft's flight logs and maintenance records showed that no mechanical discrepancies were noted for May 11, 1979. On the day of the accident, in violation of standard procedure, the records were not removed from the aircraft, and were destroyed in the accident.