The US National Transportation Safety Board has revealed that Boeing was aware of a critical flaw in an engine part years before it was implicated in a fatal UPS cargo plane crash in Louisville, Kentucky, that killed 15 people last November.
On November 4, 2025, a UPS MD-11F freighter crashed shortly after takeoff from Louisville Muhammad Ali International Airport when one of its engines separated from the wing, causing the aircraft to lose control and slam into an industrial area. The incident resulted in the deaths of three crew members and 12 individuals on the ground, with the most recent fatality occurring on Christmas Day.
According to the NTSB’s investigative update released on January 14, 2026, cracks found in the engine mounting assembly were due to fatigue in a spherical bearing race, a component that helps secure engines to wings. The board noted that Boeing had identified similar failures of this part on at least four previous occasions across three different aircraft as far back as 2011.
In response to these earlier incidents, Boeing issued a service letter in February 2011 to MD-11 operators, warning them of the defect. However, the company concluded that the issue “would not result in a safety of flight condition” and did not mandate immediate repairs. Instead, it recommended that the part be included in general visual inspections every five years, a guideline that UPS reportedly followed, with the last close inspection conducted in October 2021.
The NTSB’s findings have raised serious questions about Boeing’s safety protocols and the adequacy of its warnings. Aviation experts, including former investigators, have expressed concern that Boeing underestimated the severity of the flaw, given the critical role of the engine attachment mechanism in carrying loads such as thrust and drag. This incident echoes past criticisms of Boeing’s internal processes, notably the 737 Max crises that involved flawed software and quality control issues.
In the aftermath of the crash, UPS and FedEx temporarily grounded their fleets of MD-11 aircraft. The tragedy has also sparked legal action, with relatives of victims filing lawsuits alleging negligence for keeping the aging MD-11 in service despite known maintenance problems. The aircraft involved was 34 years old, highlighting challenges with older aviation fleets.
Boeing has issued a statement expressing condolences and affirming support for the NTSB investigation but has not directly addressed the report’s specifics. Similarly, UPS has emphasized its focus on recovery efforts and support for affected families while refraining from comment on ongoing litigation.
The NTSB’s investigation is continuing, with a final report expected to provide conclusive findings on the cause of the crash. This case underscores ongoing concerns in the aviation industry about aging aircraft maintenance, manufacturer accountability, and the effectiveness of safety communication between companies and operators.
