Having taken off that day from O' Hare, the plane carried 258 passengers and 13 crew members for its flight. 2 people on the ground would die in the upcoming incident. At 3:02 PM CDT, the aircraft began its takeoff down Runway 32R (Right).
Shortly after the takeoff roll began, tower controllers witnessed the number one engine separate from the aircraft and fly up and over the left wing. The aircraft continued in a normal climb momentarily, as fuel and leaking hydraulic fluid spewed in a vapor trail behind the doomed plane. Unknown to the pilots, the engine separation had severed the hydraulic lines that controlled the aircraft's leading-edge wing slats (retractable devices that increase a wing's lift during takeoff and landing). As the hydraulic fluid bled away, the slats retracted on the left wing, creating an asymmetrical lift condition thus allowing the left wing to lose lift while the right wing underwent increasing lift. The aircraft quickly entered an uncontrollable 112-degree bank and pitched nose-down from an altitude of 400 feet slamming into a nearby mobile home park and an open field. All 270 persons on board were fatally injured. In addition, two residents of the mobile home park also perished.
The resulting investigation by the National Transportation Safety Board revealed the probable cause to be attributable to damage to the left wing engine pylon that occurred during an earlier engine change at American's aircraft overhaul facility in Tulsa, Oklahoma. Contributing to the cause were several inoperative key instruments that would have informed the pilots of the slat's asymmetrical condition. However, the NTSB also indicated that given the circumstances of the situation, the pilots were not in any way to blame for the resulting accident.
Many problems with DC-10s were discovered as a cause of the accident, including problems in the wings and engines areas. Since this tragedy happened just after a Western Airlines DC-10 had crashed in Mexico City and six years after a Turkish Airlines DC-10 crashed in Paris, the FAA quickly ordered all DC-10s to be stored until all problems were solved. The result of the problem solving was an arguably more efficient and safe DC-10.
The crash of May 25, 1979 in Chicago remains the largest single-aircraft air crash in United States history. Another flight with the same number, Delta Air Lines Flight 191, crashed at Dallas/Fort Worth International Airport in 1985. Neither company has ever used the 191 flight number again.