Swissair Flight 306 was a scheduled international flight from Zrich to Rome, with an intermediate stop at Geneva. Dense fog was existing at the time of departure and at 07:00 hours local time the flight was informed that the RVR was 180 m for runway 34 and 60 m for runway 16, and that there was a light northerly wind (1 to 2 kt). At 07:04 hours the flight was authorized to taxi to runway 34 behind an accompanying vehicle. At 07:05 the crew reported that they would taxi half way down runway 34 to inspect the fog condition and then return to takeoff position. This was done, using at times considerable engine power probably in an attempt to disperse the fog. Around 07:12 hours the aircraft was back at the threshold of runway 34 and permission to takeoff was granted. The flight took off at 07:13 hours and started to climb to flight level 150, its cruising altitude. Four minutes later witnesses on the ground noticed a whitish trail of smoke on the left side of the aircraft and suddenly a long flame from the left wing-root. Around 07:20 hours the aircraft reached an altitude of approximately 2700 m. It then began to lose height, entered a gentle left turn loosing height more rapidly and finally went into a steep dive. Parts of the aircraft became detached and at 07:21 hours a “MAYDAY” message was received., At 07:22 hours the aircraft crashed into the ground on the outskirts of Drren„sch, at an elevation of 559 m, approximately 35 km from Zrich/Kloten Airport. PROBABLE CAUSE: “The crash was due to the destruction of essential structural parts of the aircraft by a fire caused by overheating of the brakes during the taxiing phase.”