RedBullGaveMeWings:
Just out of curiosity, on which occasion has it already happened?
One answer: B707 G-APFE, CAT Accident - Mount Fuji Japan, 5th March 1966
BOAC Flight 911 | Good and Bad Japan
"One of the passengers left an important clue behind. That person, in all the horrific terror that must surely have occurred, managed to shoot an 8mm cine film. Despite the fact that the flight data recorder was destroyed by fire, the film footage somehow survived the accident. It showed that just before the accident the plane was indeed experiencing severe turbulence. Debris was scattered over 16 kilometres. The probable cause given by the Aviation Safety Network was this: ‘The aircraft suddenly encountered abnormally severe turbulence over Gotemba City which imposed a gust load considerably in excess of the design limit'."