On November 4, 2025, about 1714 eastern standard time, United Parcel Service (UPS) flight 2976, a Boeing (McDonnell-Douglas) MD 11F airplane, N259UP, was destroyed after it impacted buildings and the ground shortly after takeoff from runway 17R at Louisville Muhammad Ali International Airport, Louisville, Kentucky. The 3 crewmembers aboard the airplane and 11 people on the ground were fatally injured. There were 23 others on the ground who were injured.
NTSB Presented the details of the structure of the MD-11F aircraft engine-to-wing attachment and presented investigative findings related to the separation of the left engine.
The engine separation sequence began with failures inside the left engine’s aft pylon mount assembly. Investigators found that fatigue cracks first developed in the spherical bearing outer race, specifically at the grease-distribution groove inside the bearing.
As the cracks expanded over time, the outer race split into two pieces. Once the bearing outer race separated, the load distribution inside the aft mount became abnormal, placing excessive stress on the mounting lugs.
This abnormal loading then caused fatigue cracks to form in both the forward and aft lugs of the aft mount. The cracks propagated through the lug bores, eventually causing:
* complete fracture on the inboard side of the lugs,
* bending deformation of the lugs,
* followed by complete fracture on the outboard side.
With the aft mount fractured, the left engine and pylon assembly were no longer securely attached at the rear. This allowed the engine to rotate upward around the remaining forward mount attachment point.
The resulting overload forces then caused failure of the forward mount as well, leading to the complete separation of the left engine and pylon assembly from the aircraft shortly after takeoff.
In summary, the failure chain was:
1. Fatigue cracks in the spherical bearing outer race
2. Outer race separation into two pieces
3. Abnormal loading on aft mount lugs
4. Fatigue cracking and fracture of aft mount lugs
5. Separation of the aft mount
6. Upward rotation of the engine/pylon assembly
7. Overload failure of the forward mount
8. Complete engine separation from the aircraft