The McDonnell Douglas DC-10 crashes of the 1970s and 1980s killed more than a thousand people and forced sweeping changes to how commercial airliners are certified, maintained, and flown. Three accidents define the aircraft’s record: Turkish Airlines Flight 981 outside Paris in 1974, American Airlines Flight 191 in Chicago in 1979, and United Airlines Flight 232 at Sioux City in 1989. Each traced back to a different failure — a defective cargo door, an unauthorized maintenance shortcut, and an uncontained engine burst — and each left the aviation safety system permanently changed.
Turkish Airlines Flight 981 and the Cargo Door Defect
On March 3, 1974, a Turkish Airlines DC-10 lost its rear cargo door shortly after takeoff from Paris-Orly. The explosive decompression collapsed the cabin floor, severed the control cables running beneath it, and killed the number 2 engine. With no way to steer, the crew flew into the Ermenonville forest. All 346 people aboard died.1FAA. Lessons Learned: TC-JAV
The latching mechanism was defective by design. It could indicate a locked door when the latches were not fully engaged and the lock pins were out of place, and high closing forces could prematurely shut the vent door that was supposed to prevent pressurization if the cargo door was unsecured.1FAA. Lessons Learned: TC-JAV
The flaw was already known. On June 12, 1972, American Airlines Flight 96 had suffered the same kind of failure over Windsor, Ontario, and only luck and a skilled crew kept it from ending like Paris. FAA inspectors had flagged the defect during certification testing as early as 1970.2Time. The DC-10 Cargo Door
The “Gentleman’s Agreement”
After Windsor, the FAA prepared a mandatory Airworthiness Directive that would have forced McDonnell Douglas to fix the door. It was never issued. Testimony before the Senate Aviation Subcommittee revealed that FAA head John H. Shaffer had asked that the corrective action be handled through a “gentlemen’s agreement” instead. The fix became a voluntary service bulletin, which airlines could adopt on their own schedule.3The New York Times. Change on DC-10 Called Optional Airworthiness directives carry the force of law; service bulletins are recommendations.
The Turkish Airlines aircraft never received the modification. McDonnell Douglas’s own records falsely indicated that the work had been done.1FAA. Lessons Learned: TC-JAV C.O. Miller of the National Transportation Safety Board told Senate investigators that manufacturers preferred voluntary measures because they could “lessen their liability to damages” in lawsuits following accidents.3The New York Times. Change on DC-10 Called Optional
The Applegate Memo
Inside the DC-10’s fuselage subcontractor, Convair Division of General Dynamics, Director of Product Engineering Dan Applegate wrote an internal memo after the Windsor incident warning that the aircraft was inherently susceptible to catastrophic failure. He called McDonnell Douglas’s service bulletins “Band-aid fixes” and identified the underlying problem as the unvented passenger floor, which would collapse during explosive decompression and destroy the flight controls routed beneath it. He predicted cargo doors would come open during the aircraft’s service life and that this would “usually result in the loss of the airplane.”4Clyde & Co. Case Studies in Engineering and Ethical Failures
Convair management did not act on the memo, fearing damage to its business relationship with McDonnell Douglas. Convair’s own internal failure analysis, which had already mapped the exact sequence that later brought down Flight 981, was never disclosed to the FAA, and McDonnell Douglas’s submissions to the agency did not mention cargo door malfunctions.4Clyde & Co. Case Studies in Engineering and Ethical Failures The memo surfaced during litigation after the Paris crash and is now a standard case study in engineering ethics.5Design News. Designed for Disaster: The DC-10 Airliner
Regulatory Response
Within 96 hours of the Paris crash, the FAA issued a telegraphic Airworthiness Directive mandating changes to the cargo door latching system. Additional directives followed, culminating in AD 75-15-05 R1, the “floors and doors” directive, which required floor reinforcement capable of surviving sudden decompression not only on the DC-10 but on the L-1011, Boeing 747, and Airbus A300 as well.1FAA. Lessons Learned: TC-JAV The FAA also rewrote certification standards for fuselage door designs, requiring direct visual inspection of locking mechanisms, redundant warning systems, and pressure relief provisions.
A proposed $100 million out-of-court settlement split liability among Turkish Airlines ($10 million), McDonnell Douglas ($70 million), and General Dynamics ($12 million); as of early 1975 the two manufacturers were resisting those figures.6The New York Times. Turkish Airlines Offers $10 Million in Crash Suits
American Airlines Flight 191 and the Chicago Grounding
On May 25, 1979, American Airlines Flight 191 lost its left engine and pylon assembly moments after lifting off from O’Hare. The aircraft rolled, stalled, and crashed into a field near the airport. All 271 people aboard and two people on the ground were killed.7FAA. Lessons Learned: N110AA Setting aside the September 11 attacks, it remains the deadliest aviation disaster on U.S. soil.8Chicago Tribune. American Airlines Flight 191
The Forklift Shortcut
The NTSB found that the engine separated because of a crack in the pylon’s aft bulkhead, and the crack came from an improper maintenance procedure. McDonnell Douglas required engines and pylons to be removed separately. American Airlines had developed its own unauthorized shortcut, using a forklift to remove and reinstall the engine and pylon as a single unit. It saved roughly 200 man-hours per aircraft and cut disconnections from 79 to 27.9Code7700. Case Study: American Airlines 191
The forklift lacked the precision the job required. During reinstallation, the combined assembly was bolted back in the wrong sequence, allowing the pylon to pivot and its rear mount to strike the wing fitting. The crack went undetected. Post-accident inspection found that 76 out of 175 pylon-and-engine removal operations performed by U.S. carriers using a forklift had resulted in impact damage or cracking. Continental Airlines had produced nearly identical damage on two aircraft in the months before the crash but never reported it to McDonnell Douglas or the FAA.9Code7700. Case Study: American Airlines 191
Design Vulnerabilities Exposed
The maintenance error started the accident, but design decisions finished it. When the engine tore away, it severed the hydraulic lines feeding the left outboard leading-edge slats. The slats had no alternate locking mechanism, so they retracted under aerodynamic loads and produced an asymmetric stall the crew could not recover from. The separation also disabled the captain’s flight instruments, the stick shaker stall warning, and the slat disagreement indicator, and there was no crossover between the left and right stall warning systems. The crew got no alert that one wing was about to stall.7FAA. Lessons Learned: N110AA
The 37-Day Grounding
On June 6, 1979, FAA Administrator Langhorne Bond revoked the DC-10’s type certificate, grounding all 138 DC-10s operated by eight U.S. carriers. It was the first time a commercial jetliner had been grounded that way. Regulators worldwide grounded another 136 aircraft.10The Air Current. Searching for 40-Year-Old Lessons for Boeing in the Grounding of the DC-10
Bond’s action came only hours after the FAA had opposed a court order that would have forced the same result. The turnabout followed inspectors finding new cracks in the engine mounts of two DC-10s that had been cleared to fly in fewer than 100 hours before.11The Washington Post. Possible Design Problem Grounds All US DC-10s The NTSB pushed back, with board members arguing that pilots were trained to fly with one engine out.12FAA. Aviation Week: Crash to Boost FAA Scrutiny
The fleet returned to service on July 13, 1979, after 37 days. Before it could fly again, the FAA issued Airworthiness Directives requiring inspection of pylon bolts, replacement of cracked hardware, installation of redundant stall warning systems drawing from both sides of the aircraft, a second stick shaker for the first officer, and a ban on the forklift removal procedure. The hydraulic system was redesigned so that leading-edge slats required hydraulic pressure to move in either direction, ruling out uncommanded retraction.7FAA. Lessons Learned: N110AA
Certification Reckoning
The crash prompted congressional alarm over how far the FAA had leaned on manufacturers to certify their own aircraft. The FAA convened a blue-ribbon panel of 13 independent experts through the National Academy of Sciences, chaired by former NASA Administrator George Low. Its 118-page report, published in June 1980, identified “critical deficiencies in the way the Government certifies the safety of American-built airliners.” The panel found that 94 percent of approval work was delegated to manufacturers and that the FAA’s internal technical competence had “fallen behind those in industry.”10The Air Current. Searching for 40-Year-Old Lessons for Boeing in the Grounding of the DC-10
The panel wrote that manufacturers often met the “letter of the law” while falling short of the “spirit of safety,” and specifically criticized McDonnell Douglas for failing to build as safe an airplane as it could have. One recommendation was that every commercial aircraft manufacturer establish an internal safety organization to provide independent assurance of airworthiness. Forty years passed before Boeing’s Board of Directors adopted that recommendation, on September 30, 2019.10The Air Current. Searching for 40-Year-Old Lessons for Boeing in the Grounding of the DC-10
United Airlines Flight 232 and the Hydraulics Problem
On July 19, 1989, United Airlines Flight 232 was cruising toward Chicago with 296 people aboard when its tail-mounted number 2 engine suffered an uncontained failure. Shrapnel from the disintegrating fan disk severed all three of the aircraft’s independent hydraulic systems. The crew was left with no conventional flight controls at all.13NTSB. Aircraft Accident Report AAR-90-06
Captain Al Haynes and his crew improvised a technique that had never been trained: steering by varying thrust between the two remaining wing engines. Captain Dennis Fitch, an off-duty United DC-10 training check airman traveling as a passenger, came to the cockpit and worked the throttles to dampen the aircraft’s oscillations and turn it toward Sioux Gateway Airport in Sioux City, Iowa.14Safety Compass. Remembering Captain Al Haynes
The DC-10 touched down at a high sink rate on runway 22, skidded, rolled inverted, and broke apart. Of the 296 aboard, 111 were killed and 47 were seriously injured; 185 survived. The NTSB called the crew’s performance “highly commendable” and said it “greatly exceeded reasonable expectations.”15FAA. Lessons Learned: N1819U
Cause
The NTSB traced the fan disk failure to a metallurgical defect present since the disk was manufactured in 1971, using a process later recognized for producing material flaws. A fatigue crack had grown from the defect but was missed at United Airlines’ engine overhaul facility. The board cited “inadequate consideration given to human factors limitations” in the inspection and quality control procedures.16NTSB. Investigation DCA89MA063
The investigation also exposed a design vulnerability. The DC-10’s three hydraulic systems were technically independent but routed in close physical proximity through the tail section, leaving all three exposed to the same single event. The debris energy from the fan disk failure exceeded the protection the design was meant to provide. The NTSB issued 29 safety recommendations covering engine inspection, backup flight controls, and cabin safety.15FAA. Lessons Learned: N1819U
The CRM Legacy
Flight 232 became a landmark in the history of Crew Resource Management. “If I hadn’t used CRM, if we had not let everybody put their input in, it’s a cinch we wouldn’t have made it,” Haynes said.14Safety Compass. Remembering Captain Al Haynes The NTSB had recommended mandatory CRM training a decade earlier, and the Sioux City accident supplied the clearest possible demonstration of its value. CRM now extends beyond the cockpit to controllers, dispatchers, and ground personnel, and is a required component of aviation training worldwide.17AOPA. Team Building in the Cockpit
Litigation and Damages
More than 200 lawsuits followed Flight 191 alone. In Illinois, 67 of those were filed, and 64 settled out of court, with settlements averaging roughly $150,000 and three exceeding $1.5 million. A jury awarded $4.1 million to Lora Lux, widow of captain Walter Lux, in 1984; the defendants appealed, arguing the amount was excessive.18Chicago Tribune. Settlement in ’79 O’Hare Crash
Plaintiffs’ attorneys pushed for punitive damages, aiming to prove McDonnell Douglas had known about the aircraft’s potential for failure. In May 1980, a federal district court allowed the punitive claims to proceed. In January 1981, the Seventh Circuit Court of Appeals reversed, holding that under Illinois law neither defendant could be sued for punitive damages in a wrongful death action.19CaseMine. In re Air Crash Disaster Near Chicago, MDL No. 391 The ruling was expected to push remaining cases toward compensatory settlements.20The Washington Post. Court Curbs McDonnell Liability Earlier in the litigation, American and McDonnell Douglas had offered a combined $30 million to the families of 112 victims in exchange for waiving punitive claims; experts at the time estimated total claims could reach $200 million.21Time. The DC-10 Crash Sweepstakes
End of the DC-10
McDonnell Douglas ended DC-10 production for airlines in 1983, and the last military variants were delivered in 1989 or 1990. The safety crises, poor fuel economy against emerging twinjets like the Boeing 767 and Airbus A300, and a general market shift made continued production untenable.22Airways Magazine. L-1011 TriStar and DC-10: Forgotten Giants Nearly 450 DC-10s were built.23San Diego Air & Space Museum. Celebrating 50 Years of the DC-10 The type is long retired from passenger service, though some DC-10s and their MD-11 derivatives kept flying into the 2020s in cargo, aerial refueling, and firefighting roles.