NTSB: Boeing Knew of MD-11F Structural Flaw Years Before Deadly UPS Crash

Federal investigators have released a critical update. The National Transportation Safety Board (NTSB) is investigating a fatal cargo jet accident. The crash involved a UPS cargo jet crash in Louisville, Kentucky. The NTSB report suggests the manufacturer, Boeing, had prior knowledge of a structural weakness. This flaw was in a key engine component. The November 2025 crash killed 15 people.

Investigation Focus: The MD-11F Flaw

The accident involved a Boeing MD-11F freighter. The MD-11 was originally built by McDonnell Douglas. Boeing acquired the company in the 1990s. The aircraft was departing Louisville Muhammad Ali International Airport (SDF). It was bound for Hawaii on November 4, 2025. Moments after takeoff, the left engine separated from the wing. The jet crashed into buildings near the airport perimeter. Three crew members died on board the aircraft. Twelve people on the ground were also killed.

Investigators quickly focused on the left engine's pylon mount. This assembly secures the engine to the wing. The NTSB found evidence of fatigue cracks in the part. Specifically, the spherical bearing assembly had fractured. This bearing race broke into two pieces.

Prior Knowledge and Service Letters

The most concerning finding relates to Boeing's knowledge. The NTSB cited a 2011 Boeing service letter. This letter warned operators about the issue. Boeing had documented at least four prior failures of this part. These failures occurred on three different MD-11 aircraft.

Crucially, the 2011 letter stated the fractures “would not result in a safety of flight condition”. Boeing did recommend visual inspections. These inspections were advised every five years. However, the company did not prohibit the older design. The flawed design included a recessed groove. This groove was where the fatigue cracks originated.

Airworthiness and Maintenance Concerns

The MD-11F involved in the Louisville fatal accident had been inspected. Records show the component was last checked in October 2021. This was approximately four years before the crash. The NTSB noted the plane was not due for its next detailed inspection. The existing maintenance schedule did not catch the cracks. This raises serious questions about cargo aircraft maintenance protocols.

• The failed part was an engine pylon structural weakness.
• Boeing documented four prior failures in 2011.
• The manufacturer initially deemed the issue safe for flight.
• The MD-11F was not due for a detailed inspection.

Following the crash, major industry action was taken. Boeing recommended grounding all MD-11s. UPS and FedEx, major MD-11F operators, also grounded their fleets. The Federal Aviation Administration (FAA) temporarily barred the model from flying. This was due to concerns over another engine separation.

Industry Impact and Future Directives

This ongoing aviation safety investigation highlights key challenges. It underscores the difficulty of managing older airframes. The MD-11 is a workhorse in the global cargo fleet. The NTSB's findings could lead to a mandatory airworthiness directive. Such a directive would require immediate fleet-wide action.

Regulators will likely review inspection requirements. The focus will be on the spherical bearing assembly. The final NTSB report will determine the probable cause. This determination is expected within two years of the accident. The findings will shape future maintenance and design standards. This is especially true for older aircraft designs.

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