The US National Transportation Safety Board (NTSB) said in a report released on Wednesday that the UPS cargo plane that crashed in Louisville, Kentucky, in November, killing 15 people, had a structural flaw that manufacturer Boeing had previously concluded would not affect the safety of the flight.
The NTSB said cracks in the assembly holding the left engine in place may have contributed to the November crash, although it has not yet officially pinpointed a cause. According to the report, the part had failed in similar ways on at least four other occasions in three different planes, citing a service bulletin Boeing issued in 2011 about the apparent failure.
In the service bulletin — a document used by manufacturers to alert aircraft owners about safety issues or other problems — Boeing said the fractures “would not result in a condition that would affect the safety of flight,” NTSB investigators wrote.
The plane that crashed was an MD-11F jet, manufactured by McDonnell Douglas, a company acquired by Boeing in the 1990s. The aircraft was taking off from Louisville to Hawaii on November 4, when a fire started in its left engine shortly after takeoff.
The plane crashed into several buildings, including a petroleum recycling facility, near Louisville Muhammad Ali International Airport. The three crew members on board and 11 people on the ground died in the crash; a 12th person on land died from injuries suffered in the episode.
In a statement, a Boeing representative said the company supports the NTSB investigation and expressed condolences to the families of the victims. The company, one of the largest aircraft manufacturers in the world, has been under pressure in recent years due to concerns over its quality control. She did not specifically comment on the report’s findings in her note.
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After the accident, Boeing recommended that all MD-11s be grounded while the NTSB conducted its investigation. UPS also announced that it would remove its fleet of MD-11s from service, and the Federal Aviation Administration (FAA) issued a temporary ban on flights of that model, citing concerns that a similar engine retirement “could result in the loss of safety of continued flight and landing.”
In an initial report released in November, NTSB investigators noted that portions of the bearing assembly connecting the left engine to the cargo plane’s wing had ruptured and showed signs of “fatigue cracking” and “overload failure.” According to the most recent NTSB report, Boeing had recommended in its service bulletin that the part be inspected every 60 months as part of a general visual inspection.
The NTSB’s preliminary report indicated that UPS’s policy was to inspect the part as part of a general visual inspection every 72 months, and that it had last been examined on October 28, 2021 — about 49 months before the accident. The preliminary report also recorded that the bearings had been lubricated about two weeks before the crash, on October 18, 2025.
The preliminary report also stated that the “lugs” (ears/flaps) that kept the part in place — also fractured — and other coupling devices should only undergo a special inspection after a few thousand more takeoff and landing cycles.
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