Boeing warned plane owners in 2011 about a broken part that contributed to a UPS plane crash that killed 15 last year but at that point the planemaker didn’t believe it threatened safety, the National Transportation Safety Board said Wednesday.

The UPS plane crashed in November 2025 shortly after taking off in Louisville, when the left engine flew off the wing as the plane rolled down the runway.

The NTSB said Wednesday that Boeing had documented in 2011 there were four previous failures of a part that helps secure the MD-11’s engines to the wings on three different planes, but at that point the planemaker “determined it would not result in a safety of flight condition.” NTSB didn’t say whether there had been additional documented failures of the spherical bearing race since 2011.

Photos released by the NTSB of the Nov. 4 crash show flames erupting as the rear of the engine starting to detach before it flew up and over the wing. Then the wing was engulfed by fire as the burning engine flew above it.

Three pilots on the plane that was headed for Hawaii were killed along with 12 more people on the ground near Louisville’s Muhammad Ali International Airport.

The NTSB previously said investigators found cracks in some of the parts that held the engine to the wing. Those cracks hadn’t been caught in regular maintenance done on the plane, which raised questions about the adequacy of the maintenance schedule. The last time those key engine mount parts were examined closely was in October 2021, and the plane wasn’t due for another detailed inspection for roughly 7,000 more takeoffs and landings.

The 34-year-old MD-11 plane only got 30 feet (9.1 meters) off the ground before crashing into several industrial buildings just past the runway and generating a massive fireball that could be seen for miles. Dramatic videos of the crash showed the plane on fire as it plowed into buildings and released a massive plume of smoke.

Airlines quit flying this type of plane commercially years ago, but they had continued to fly for cargo carriers like UPS and FedEx and a few of these planes were also modified for use in firefighting. All the MD-11s that had been in use and 10 related DC-10s have been grounded since the crash.

It’s not clear when the cracks started to develop in the engine mounting pylon, but this crash is reminiscent of a 1979 crash in Chicago when the left engine flew off an American Airlines DC-10 during takeoff, killing 273 people. The DC-10 was the predecessor of the MD-11.

That previous crash led to the worldwide grounding of 274 DC-10s. The airline workhorse was allowed to return to the skies because the NTSB determined that maintenance workers damaged the plane that crashed while improperly using a forklift to reattach the engine. That meant the crash wasn’t caused by a fatal design flaw even though there had already been a number of accidents involving DC-10s.

Josh Funk, The Associated Press