A drone view of the crash site next to a runway at the Muhammad Ali International Airport following the crash of a UPS cargo plane in Louisville, Kentucky, U.S., in this screengrab from a video released November 7, 2025. NTSB/Handout via REUTERS

By David Shepardson and Allison Lampert

WASHINGTON (Reuters) -The National Transportation Safety Board said on Thursday it has found evidence of fatigue cracks in a key part of a crashed UPS MD-11 cargo jet that killed 14 people in Louisville, Kentucky, on November 4.

The bulk of the left engine pylon, a structural component connecting the aircraft engine to the wing or fuselage, was still attached to the left engine when it separated from the wing. The NTSB said it found evidence of fatigue cracks in the left pylon aft mount lug.

UPS and FedEx both grounded their MD-11 fleets this month as a precaution and at the recommendation of U.S. planemaker Boeing. The Federal Aviation Administration also issued directives that temporarily grounded the MD-11 and the DC-10 due to their similar design.

The preliminary report referenced the crash of an American Airlines DC-10 jet in May 1979, which it listed under “similar events.” During the takeoff rotation of Flight 191 from Chicago O’Hare Airport, the left engine and pylon assembly, and about three feet of the leading edge of the left wing, separated from the airplane and fell to the runway.

U.S. safety investigators have said they are probing the maintenance history of the 34-year-old UPS cargo plane that was in Texas for repairs weeks before crashing in flames after takeoff.

NTSB Chair Jennifer Homendy told Reuters this week that Boeing is doing some additional modeling and testing as part of the investigation. Boeing has owned the broader MD-11 program since its 1997 merger with McDonnell Douglas.

For cargo, there are about 50 MD-11 planes operated by FedEx and UPS worldwide.

(Reporting by David Shepardson and Allison LampertEditing by Rod Nickel)