Boeing warned aircraft owners in 2011 about a component that later failed in last year’s deadly UPS cargo plane crash, but at the time did not consider it a flight safety threat, the National Transportation Safety Board said Wednesday.
The UPS MD-11 cargo plane crashed in November 2025 shortly after takeoff from Louisville, Kentucky, when its left engine separated from the wing. The aircraft, bound for Hawaii, was traveling close to 200 mph and carrying thousands of packages and tens of thousands of gallons of fuel. The crash killed all three crew members and 12 people on the ground near Louisville Muhammad Ali International Airport.
According to the NTSB, Boeing documented four previous failures of a part known as the spherical bearing race — which helps secure the engine to the wing — on three MD-11 planes in 2011. However, Boeing concluded at the time that the issue would not create a “safety of flight condition.” The MD-11 was originally built by McDonnell Douglas, which Boeing later acquired.
Investigators previously reported finding cracks in engine-mount components that were not detected during routine maintenance. The last detailed inspection of those parts occurred in October 2021, and the aircraft was not scheduled for another for roughly 7,000 more flight cycles.
The crash has drawn comparisons to a 1979 American Airlines DC-10 disaster in Chicago, when an engine detached during takeoff, killing 273 people. That incident led to the global grounding of DC-10s. Aviation experts note that a McDonnell Douglas bulletin issued after that crash labeled similar bearing failures as a serious safety concern.
Former investigators say Boeing’s 2011 service bulletin — which did not mandate repairs and was not enforced by an FAA airworthiness directive — raises questions about whether the response was sufficient. Investigators are also reviewing how UPS incorporated the guidance into its maintenance practices.
The NTSB’s factual report does not determine the cause of the engine separation, but investigators are focused on the bearing failure. A final report is expected in more than a year and is likely to play a key role in lawsuits already filed over the crash.
The 34-year-old aircraft lifted only about 30 feet off the ground before slamming into nearby industrial buildings, triggering a massive fireball. Since the crash, all MD-11s and several related DC-10 aircraft have been grounded.
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