The UPS MD-11 freighter that crashed in Louisville on November 4, killing 14 people, failed to achieve a normal climb rate and showed evidence of fatigue cracks, according to a preliminary report from the National Transportation Safety Board, reported London's Air Cargo News.

The aircraft, operating domestic cargo flight 2976, climbed only about 30 feet before losing altitude. Witnesses said the takeoff speed appeared normal but the climb rate was not, with the plane rolling slightly left before descending.

Airport surveillance video showed the left engine and pylon separating from the wing shortly after rotation, igniting a fire before striking the ground. The aircraft then impacted several buildings.

Investigators found stress fractures on components of the aircraft. Examination of the left pylon aft mount lug revealed fatigue cracks alongside overstress failures, with cracks observed on both inboard and outboard fracture surfaces.

The MD-11's left and right engines are mounted beneath pylons attached to each wing, while the centre engine is fixed to the vertical stabiliser. The report confirmed the flight crew had received and acknowledged takeoff clearance.