This article is based on an official investigative update from the National Transportation Safety Board (NTSB) regarding the crash of UPS Flight 2976.

NTSB Update: Metal Fatigue in Engine Mount Cited in Fatal UPS MD-11F Crash

On January 14, 2026, the National Transportation Safety Board (NTSB) released a pivotal investigative update regarding the catastrophic crash of UPS Flight 2976. The accident, which occurred on November 4, 2025, involved a Boeing MD-11F cargo aircraft that crashed shortly after takeoff from Louisville Muhammad Ali International Airport (SDF), resulting in 14 fatalities and significant ground injuries.

The latest findings from federal investigators identify metal fatigue in a critical engine mount component as the primary factor leading to the separation of the aircraft’s left engine. This update connects the tragic event to a specific design issue that had been flagged in a Boeing service letter nearly 15 years prior, raising new questions about maintenance intervals and fleet safety for the aging tri-jet freighter.

Metallurgical Findings: The Spherical Bearing Assembly

According to the NTSB’s six-page update, the investigation has focused heavily on the metallurgical examination of the aircraft’s left pylon structure. The report confirms that the left engine (No. 1) and its pylon detached from the wing moments after the aircraft rotated for takeoff. The separation was triggered by the fracture of the spherical bearing assembly located in the left pylon’s aft mount bulkhead.

Laboratory analysis detailed in the update reveals that the failure was not instantaneous but the result of progressive degradation. Investigators found that fatigue cracking covered approximately 75% of the fracture surface on the bearing race. The remaining portion of the component failed due to overstress once the weakened structure could no longer support the engine’s load.

“The fatigue cracking originated around the circumference of the bearing race at a design recess groove… leading to the separation of the left engine and pylon shortly after takeoff.”

, National Transportation Safety Board (NTSB), Investigative Update DCA26MA024

Link to 2011 Service Letter

The NTSB noted that the design of the failed bearing assembly corresponds to a part previously cited in a Boeing Service Letter dated February 7, 2011. That document had recorded four similar bearing race failures on three other MD-11 aircraft. At the time, however, the manufacturer did not classify the issue as a “safety of flight” condition, a classification that is likely to face renewed scrutiny in light of the Louisville disaster.

Accident Sequence and Impact

The sequence of events on November 4, 2025, describes a normal takeoff roll that turned catastrophic immediately upon rotation. Surveillance video reviewed by the NTSB shows the left engine breaking free, traveling over the fuselage, and striking the ground. A fire erupted instantly at the wing-pylon attachment point.

Stripped of thrust and aerodynamic stability, the aircraft struggled to climb, reaching a maximum altitude of only approximately 30 feet above ground level (AGL). The MD-11F cleared the airport blast fence but its landing gear impacted the roof of a UPS Supply Chain Solutions warehouse. The aircraft subsequently crashed into a nearby industrial park, striking a petroleum recycling facility.

The crash resulted in the deaths of all three crew members, the Captain, First Officer, and Relief Captain, as well as 11 individuals on the ground. Another 23 people in the industrial park sustained injuries.

Fleet Status and Regulatory Response

The crash of UPS Flight 2976 has triggered immediate repercussions across the air cargo industry. Following the accident, UPS grounded its entire MD-11 fleet, which constitutes approximately 9% of its total aircraft, “out of an abundance of caution.” FedEx, another major operator of the type, also grounded its fleet to conduct safety reviews.

In response to the preliminary findings, the Federal Aviation Administration (FAA) issued Emergency Airworthiness Directives (ADs) for MD-11 and DC-10 series aircraft. These directives mandate immediate inspections of pylon thrust links and spherical bearings.

Maintenance Timeline Discrepancies

The NTSB update highlights a concerning gap in the maintenance timeline. The accident aircraft, registered as N259UP, had accumulated 21,043 flight cycles since its manufacture in 1991. Maintenance records indicate the aircraft underwent a lubrication task for the pylon thrust links and bearings on October 18, 2025, less than a month before the crash.

However, the “special detailed inspection” (SDI) designed to detect the specific type of fatigue cracking found in the wreckage was not yet due. The current maintenance schedule calls for this inspection at 29,200 cycles. The aircraft failed roughly 8,000 cycles before it would have reached that mandatory inspection point.

AirPro News Analysis

The disparity between the failure point (21,043 cycles) and the inspection interval (29,200 cycles) suggests a potential blind spot in the legacy maintenance programs for the MD-11. While the 2011 Boeing Service Letter identified the potential for failure, the lack of a “safety of flight” designation may have delayed the implementation of more aggressive inspection protocols.

We anticipate that the NTSB’s final report will likely recommend a significant reduction in inspection intervals for these components. For operators like UPS and FedEx, this could mean more frequent, invasive maintenance checks for their aging tri-jet fleets, potentially accelerating the retirement of the MD-11 type from frontline cargo service.

Investigation Status

The NTSB investigation remains ongoing, with a final Probable Cause report expected within 12 to 24 months. Current investigative efforts are focused on why the fatigue cracks went undetected during the October 2025 maintenance and evaluating the survivability factors regarding the fire spread in the industrial park.

Parties to the investigation include the FAA, UPS, Boeing, the Independent Pilots Association (IPA), General Electric (GE) Aerospace, and the Teamsters Airline Division.

Sources:

• NTSB Investigative Update (DCA26MA024)
• NTSB website
• Boeing Service Letter (Feb 7, 2011)