NTSB Notes Pylon Lug Fatigue in UPS MD-11F Accident

A structural failure in the left engine pylon of a UPS McDonnell Douglas MD-11F likely led to the separation of the No. 1 engine just after rotation in the UPS Flight 2976 crash on November 4, according to the NTSB preliminary report. Airport surveillance imagery reviewed by investigators showed the engine and pylon breaking away from the left wing and arcing over the fuselage while on fire as the airplane rotated and attempted to climb.

The aircraft reached no more than about 30 feet agl before striking a UPS warehouse beyond the end of Runway 17R at Louisville Muhammad Ali International Airport (KSDF). The MD-11F, registered as N259UP, was destroyed in subsequent impacts and fire. All three crewmembers and 11 people on the ground were killed, and 23 others on the ground were injured, two seriously.

Examination of the left pylon mounts revealed multiple structural failures. The NTSB reported that both forward and aft lugs of the left pylon’s aft mount had fractured, with investigators identifying “evidence of fatigue cracks in addition to areas of overstress failure.” On the aft lug, fatigue cracks appeared “where the aft lug bore met the aft lug forward face,” while the forward lug’s inboard surface also showed fatigue along the bore, according to the Safety Board. The forward lug’s outboard surface displayed only overstress features. The spherical bearing housed in the aft mount had fractured circumferentially, exposing the internal ball element.

Although the left pylon aft mount is subject to periodic general and detailed visual inspections, the aircraft was not yet due for the next set of special detailed inspections involving the aft mount lugs and wing clevis, which trigger at higher cycle counts. Records showed the last visual inspection of the mount occurred in October 2021, and a required lubrication task for the thrust links and spherical bearings had been completed on Oct. 18, 2025, just weeks before the accident.

The NTSB recovered both the cockpit voice recorder (CVR) and flight data recorder (FDR) and the data from both devices has been downloaded. Agents are analyzing the recordings, along with metallurgical examinations and systems data, as the investigation continues.

On the recommendation of Boeing, UPS grounded its MD-11 fleet, which the company identified as representing 9% of its aircraft fleet, on November 7, stating the action was taken “out of an abundance of caution.” In related and subsequent statements, the company expressed condolences and emphasized its cooperation with the investigation, noting that safety remains its highest priority. A November 20 company statement reiterated the note about MD-11s being grounded. 

The FAA followed with Emergency Airworthiness Directive 2025-23-51 on November 8, prohibiting further flight of MD-11s and MD-11Fs until operators completed inspections and any corrective actions approved by the agency’s Continued Operational Safety Branch. A superseding directive issued November 14 widened the scope to include DC-10-series aircraft due to their similar pylon architecture.

In its report, the NTSB noted similarities with the 1979 crash of American Airlines flight 191, a McDonnell-Douglas DC-10-10 that crashed at Chicago O’Hare International Airport (KORD). The NTSB’s investigation of Flight 2976 remains ongoing as investigators continue reviewing structures, materials, maintenance records, operational factors, and flight-recorder information.