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. The McDonnell Douglas DC-10-10 crashed on May 25, 1979, moments after takeoff from Chicago. All 258 passengers and 13 crew on board were killed, along with two 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 left wing stalled while the right wing, with its slats still deployed, continued to produce lift. The jetliner subsequently rolled 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.
While maintenance issues and not the actual design of the aircraft were ultimately found responsible for the crash, the accident and subsequent grounding of all DC-10s by the Federal Aviation Administration added to an already unfavorable reputation of the DC-10 aircraft in the eyes of the public, caused by several other incidents and accidents involving the type. The investigation also revealed other DC-10s with damage caused by the same faulty maintenance procedure. The faulty procedure was banned, and the aircraft type went on to have a long passenger career. It has since found a second career as a cargo airplane.