What happened
During the takeoff roll, the left number 2 main tire experienced a failure where the tread separated from the casing. Fragments of the failing tire struck the aircraft, with one portion penetrating the number one engine and another section puncturing the left wing.
Due to significant vibration caused by the damage, the crew operated the number one engine at reduced power. After performing a fuel dump, the flight returned to the departure airport. The crew executed a precautionary landing, after which passengers were deplaned and transported to the terminal via bus.
The investigation
The aircraft sustained foreign object damage (FOD) to the number one engine and developed holes in the lower wing skin near the left main landing gear wheel well. A laboratory examination of the failed tire revealed that the separation was caused by fatigue resulting from overheating, which was a consequence of the tire having undergone multiple retreadings.