1979-05-25
American Airlines
Flight AA191
Departure
Chicago O'Hare International Airport, Chicago, USA
Destination
Los Angeles International Airport, Los Angeles, USA
Causation Breakdown
Recurrence Likelihood Today
Very Low
Pylon maintenance procedures are now strictly mandated across all aircraft types. Slat disagreement warning systems are independent of engine hydraulics. Modern flight control computers provide active protection against asymmetric lift loss. A direct repeat of this failure chain is considered very unlikely.
Summary
AA191 remains the deadliest aviation accident on U.S. soil. The engine and pylon separated in one piece on the takeoff roll — a visible event witnessed by hundreds of passengers and onlookers. The crew had no way to know the slats had retracted and followed the wrong emergency procedure. A maintenance shortcut that saved time introduced a crack that killed 273 people. The crash triggered the longest grounding of a commercial aircraft type in American history.
Cause & Investigation
Determined cause
Engine separation on takeoff
The left engine and pylon assembly separated from the wing during takeoff roll. The separation sliced hydraulic lines and caused the left-wing leading-edge slats to retract, drastically reducing lift on that side. The aircraft banked left and rolled inverted at just 300 feet, with no altitude to recover. The separation was caused by a fatigue crack introduced during a maintenance procedure that used a forklift instead of the specified equipment.
Investigation body
National Transportation Safety Board (NTSB), United States.
Timeline & Safety Improvements
Flight AA191 disaster
McDonnell Douglas DC-10-10 operating for American Airlines. 273 fatalities, 0 survivors.
Formal investigation opened
Conducted by: National Transportation Safety Board (NTSB), United States.
Cause determined: Engine separation on takeoff
The left engine and pylon assembly separated from the wing during takeoff roll. The separation sliced hydraulic lines and caused the left-wing leading-edge slats to retract, drastically reducing lift on that side. The aircraft banked left and rolled inverted at just 300 feet, with no altitude to recover. The separation was caused by a fatigue crack introduced during a maintenance procedure that used a forklift instead of the specified equipment.
Improvement implemented
FAA grounded all DC-10s for 37 days — the longest grounding of a U.S. aircraft type — for pylon and engine mount inspections.
Improvement implemented
Maintenance procedures for engine pylon removal were rewritten and strictly mandated.
Improvement implemented
Using forklifts or non-approved equipment for engine pylon maintenance was explicitly prohibited.
Improvement implemented
FAA introduced new structural inspection requirements for pylon attachment points across all widebody aircraft.
Improvement implemented
Cockpit warning systems were improved to provide clearer indication of differential leading-edge slat positions.