Boeing Warned of MD-11 Parts Failure Risk in 2011, NTSB Finds

Still images from airport security footage shows UPS Flight 2976's left engine separating and moving over the aircraft as the MD-11 rotates 

The part that failed and triggered the engine separation at the heart of last November’s fatal crash of a UPS MD-11 was flagged for inspections by Boeing in 2011, but the manufacturer concluded that a worst-case failure scenario would not “result in a safety of flight condition,” the NTSB said Jan. 14.

In a mid-investigation update, the board revealed that a February 2011 Boeing service letter targeted the part, a bearing race that is part of the MD-11 engine-to-pylon mounting assembly, for repetitive inspections. The service letter detailed four failures of the part, which is part of a spherical bearing assembly, on three different airplanes.

In each case, the collar-like bearing race suffered fatigue cracking and split along its circumference. “Specifically, each failure had initiated at the design recess groove on the interior surface of the bearing race,” the NTSB update said.

“According to the service letter, a review of the spherical bearing failure by Boeing determined it would not result in a safety-of-flight condition,” the NTSB said.

But investigators found the same failure pattern on the McDonnell-Douglas-designed UPS MD-11’s No. 1 (left) engine bearing race, the report revealed.

Boeing’s letter instructed operators to inspect the bearing as part of routine, repetitive pylon mount inspections, normally every 60 months. It also updated the MD-11 maintenance manual to reflect the new inspections. Boeing also recommended installing a different bearing that does not include a groove. But it does not caution against using an airworthy grooved bearing to replace an unserviceable one of the same design.

“Investigators are reviewing” what if any steps UPS took as well as “the correspondence history” between Boeing and the FAA leading up to the 2011 letter.

Boeing purchased McDonnell-Douglas in 1997 and assumed responsibility for the continued operational safety of the former manufacturer’s in-service fleet.

It is not clear if UPS integrated the checks into its maintenance program, NTSB said.

On Nov. 4, 2025, the UPS MD-11, operating as Flight 2976, had its No. 1 engine separate from the aircraft during its takeoff roll while departing on Louisville International Airport’s runway 17 Right. The severed engine passed over the MD-11’s left wing before the aircraft rotated.

Once airborne, the MD-11 could not climb beyond about 100 ft. above ground level. It crashed about 0.5 nm from the runway end, into an industrial area. All three crewmembers and 11 people on the ground were killed.

Boeing immediately urged operators to ground their MD-11s—a move the FAA mandated.