What happened
On the morning of the accident, Flight SR-306 was operating a scheduled service from Zürich to Rome with a planned stop in Geneva. At the time of departure, the area was experiencing heavy fog, with visibility reported as low as 60 meters on runway 16 and 180 meters on runway 34. Following instructions to taxi behind a follow-me vehicle, the crew decided to taxi halfway down runway 34 to assess the fog conditions. During this maneuver, the aircraft utilized significant engine thrust, likely in an effort to clear the fog from the runway surface.
After returning to the takeoff position, the aircraft type (unspecified model) was cleared for departure at 0612 hours and lifted off at 0613 hours. The flight began a climb toward its assigned cruising altitude of flight level 150. Approximately four minutes into the climb, observers on the ground spotted white smoke trailing from the left side of the plane, followed by a large flame emerging from the left wing root.
At roughly 0620 hours, while at an altitude of about 2700 meters, the aircraft began a descent characterized by a gentle left turn and increasing loss of altitude, eventually transitioning into a steep dive. As the plane descended, structural components began to separate from the airframe. A distress signal was broadcast at 0621 hours. One minute later, the aircraft struck the ground near Dürrenäsch at an elevation of 559 meters. The impact caused the aircraft to disintegrate, resulting in 80 fatalities, which included all passengers and crew as well as 43 residents of the village of Humlikon.
Findings
The investigation determined that the accident was caused by overheating brakes during taxiing, which ignited a fire that destroyed critical structural components of the aircraft.