American Airlines Flight 191 was a regularly scheduled passenger flight operated by American Airlines from O'Hare International Airport in Chicago to Los Angeles International Airport. A McDonnell Douglas DC-10-10 used for this flight on May 25, 1979, crashed moments after takeoff from Chicago. All 258 passengers and 13 crew on board were killed, along with 2 people on the ground. It is the deadliest aviation accident to have occurred in the United States.
Investigators found that as the jet was beginning its takeoff rotation, engine number one on the left wing separated and flipped over the top of the wing. As the engine separated from the aircraft, it severed hydraulic fluid lines that locked the wing leading edge slats in place, and it damaged a three-foot section of the left wing's leading edge. Air loads on the wing resulted in an uncommanded retraction of the outboard slats. As the jet attempted to climb, the damaged left wing, producing far less lift stalled while the right wing, with its slats still deployed, continued to produce lift. The extremely disrupted and unbalanced aerodynamics of the aircraft caused it to subsequently roll 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 rigging structure holding the engine to the wing, caused by faulty maintenance procedures at American Airlines.