Korean Air Lines’ Boeing 777-3B5 performing flight KAL/KE2708 from Tokyo/Haneda, Japan to Seoul/Gimpo, South Korea rejected takeoff on runway 34R of Haneda due to a No.1 engine fire. The airplane stopped on the runway at the intersection C5, about 1500m down of 3360m long runway , with spread debris and trace of the brakes in the last 700m. The flight crew used two extinguishing bottles on engine no.1 to put out the fire. At 12:43, five minutes after the aircraft came to a stop, the flight crew ordered an evacuation since they received a new fire indication for engine no.1. All 319 onboard were evacuated on the runway using emergency slides from right side doors. No serious injuries were found among 302 passengers and 17 crew members, however, 19 had medical treatments for smoke inhalation and/or bruises during evacuation, 12 sent to hospital. The accident runway were closed for five and a half hours, and three remaining runways were also closed for two hours. This incident caused more than 400 of other commercial flights to be cancelled, as well as many more diversions, delays and returns to the destination. Probable Causes It is highly probable that the causes of this accident were the fracture of the high pressure turbine (HPT) disk of the No.1 (left-side) engine during the takeoff ground roll, the penetration of the fragment through the engine case and the occurrence of subsequent fires. Regarding the cause for the 1st stage HPT disk to be fractured, it is probable that a step was machined exceeding the allowable limit when machining U-shaped groove on the aft side of the 1st stage HPT disk to manufacture the engine and from this step the low-cycle fatigue crack was initiated and propagated during running of engine. Regarding why the step could not be found, it is somewhat likely that defects failed to be detected at the time of the inspection by the manufacturer during the production process. And as for the cracks that were not found, it is somewhat likely that those cracks failed to be detected at non-destructive inspection on the disk by the Company at the time of maintenance of the engine in use. Regarding the fire breakout from the No.1 engine, it is probable that due to the impact forces generated by the release of the fragment from the ruptured rim part of the 1st stage HPT disk through the engine case and the engine rundown loads generated when the engine stopped suddenly, the cracks were developed in the outer case of the Fuel Oil Heat Exchanger and the fuel and engine oil leaking through these cracks contacted the hot area of engine cases of the No.1 engine to be ignited.