Boeing warned plane owners in 2011 about a faulty part that was later tied to the deadly UPS cargo plane crash -- but the company did not view it as a safety risk at the time, according to the National Transportation Safety Board (NTSB).

The NTSB on Wednesday released the update amid an ongoing investigation into the crash of UPS Airlines Flight 2976 crash, revealing early evidence of long-term structural fatigue in a critical engine mount component.

Flight 2976, a McDonnell Douglas MD-11F cargo jet operated by UPS, was destroyed shortly after takeoff from Louisville Muhammad Ali International Airport on November 4, 2025.

All three crew members aboard and 12 people on the ground were killed -- and several others were hurt -- when the plane crashed into a nearby industrial area. A child was among the dead.

The NTSB said Boeing had documented more than 15 years ago 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 plane manufacturer "determined it would not result in a safety of flight condition." The planes were built by McDonnell Douglas, which was later bought by Boeing.

According to the NTSB, investigators have focused closely on the left pylon aft mount -- a key structural linkage that secures an engine to the wing. Examination of fractured components recovered at the crash site showed signs of metal fatigue cracks in multiple areas of the mount assembly. Portions of the fracture surfaces on the aft mount exhibited evidence of long-term cracking, while other regions showed failure due to overstress during the accident sequence.

The pylon and related hardware have been transported to the NTSB Materials Laboratory for further analysis as part of the systematic examination of the wreckage. The tests aim to better understand how the fatigue cracks developed and whether they played a causal role in the catastrophic separation of the engine and loss of aircraft control.

"The failure of these spherical bearing assemblies was visually identified by observing the displacement of the fractured bearing race pieces beyond the outer surface of the lugs," the NTSB said. "According to the Service Letter, a review of the spherical bearing failure by Boeing determine it would not result in a safety of flight condition."

Investigators are also reviewing flight recorder data and other evidence to reconstruct the sequence of events in the final moments before the crash, a complex process that will continue for months. The preliminary findings represent early stages of the NTSB’s work, and all details in the update remain subject to change as new information emerges.

The NTSB has not yet issued a probable cause determination, and the timeline for a final report typically spans up to two years from the date of an accident. That report is expected to include safety recommendations aimed at preventing similar tragedies in the future.

This investigation highlights ongoing concerns about aging aircraft structures and inspection practices, particularly in older freighter fleets where fatigue and wear can accumulate over decades of service. Aviation safety experts say the final outcomes could have implications for industry maintenance standards and oversight.

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EDITOR'S NOTE: The Associated Press contributed to this report.