United Airlines Flight 232 was a regularly scheduled United Airlines flight from Stapleton International Airport in Denver to O'Hare International Airport in Chicago, continuing to Philadelphia International Airport in Philadelphia, United States. On July 19, 1989, the DC-10 (registered as N1819U) serving the flight crash-landed at Sioux Gateway Airport in Sioux City, Iowa, after suffering a catastrophic failure of its tail-mounted engine due to an unnoticed manufacturing defect in the engine's fan disk, which resulted in the loss of all flight controls. Of the 296 passengers and crew on board, 112 died during the accident. while 184 people survived. Thirteen passengers were uninjured. As of 2025 it is the deadliest aviation accident to have occurred in Iowa.
Despite the fatalities, the accident is considered a good example of successful crew resource management, still a relatively new concept at the time. Contributing to the outcome was the crew's decision to recruit the assistance of a company check pilot, on board as a passenger, to assist controlling the aircraft and troubleshooting of the problem the crew was facing. 76  A majority of those aboard survived; experienced test pilots in simulators were unable to reproduce a survivable landing. It has been termed "The Impossible Landing" as it is considered one of the most impressive landings performed in the history of aviation.
The airplane, a McDonnell Douglas DC-10-10 (registration N1819U), was delivered in 1971 and owned by United Airlines since then. Before departure on the flight from Denver on July 19, 1989, the airplane had been operated for a total of 43,401 hours and 16,997 cycles (takeoff-landing pairs). The aircraft was equipped with three General Electric CF6-6D high-bypass turbofan engines produced by General Electric Aircraft Engines (GEAE). The aircraft's No. 2 (tail-mounted) engine had accumulated 42,436 hours and 16,899 cycles of operating time immediately prior to the accident flight.
The DC-10 used three independent hydraulic systems, each powered by one of the aircraft's three engines, to power movement of the aircraft's flight controls. In the event of loss of engine power or primary pump failure, a ram air turbine could provide emergency electrical power for electrically powered auxiliary pumps. These systems were designed to be redundant, such that if two hydraulic systems were inoperable, the one remaining hydraulic system would still permit the full operation and control of the airplane. However, at least one hydraulic system must have fluid present and the ability to hold fluid pressure to control the aircraft. Like other widebody transport aircraft of the time,[1]: 100  the DC-10 was not designed to revert to unassisted manual control in the event of total hydraulic failure.[1]: 17  The DC-10's hydraulic system was designed and demonstrated to the Federal Aviation Administration (FAA) as compliant with regulations that "no single [engine] failure or malfunction or probable combination of failures will jeopardize the safe operation of the airplane..."
Crew
Flight 232's captain, Alfred C. "Al" Haynes, 57, was hired by United Airlines in 1956. He was highly experienced and had 29,967 hours of total flight time with United, of which 7,190 were in the DC-10.
Haynes' co-pilot was First Officer William R. "Bill" Records, 48. He estimated that he had approximately 20,000 hours of total flight time. He was hired first by National Airlines in 1969. He worked subsequently for Pan American World Airways. He was hired by United in 1985, and had accrued 665 hours as a DC-10 first officer while at United.
Flight engineer[c] Dudley J. Dvorak, 51, was hired by United Airlines in 1986. He estimated that he had about 15,000 hours of total flying time. While working for United, he had accumulated 1,903 hours as a flight engineer in the Boeing 727 and 33 hours as a flight engineer in the DC-10.

Dennis E. Fitch, nicknamed "Denny", 46, was a training check pilot aboard Flight 232 as a passenger. He had studied the crash of Japan Air Lines Flight 123 which suffered a total hydraulic system failure and loss of flight controls and had practiced similar situations in a flight simulator.  He was hired by United in 1968 and he estimated that, prior to working for United, he had accrued at least 1,400 hours of flight time with the Air National Guard, with a total flight time around 23,000 hours. His total DC-10 time with United was 2,987 hours, including 1,943 hours accrued as a flight engineer, 965 hours as a first officer, and 79 hours as a captain.
Eight flight attendants were also aboard the flight.