Last year Air France flight 447 disappeared over the south Atlantic. No distress calls, just gone. After a year long search of deep sea bottom, the wreck was located and the flight recorders were recovered from 10,000 feet. They must build 'em right cause after a year on the bottom of the ocean, they still work.
The flight recorders reveal that the aircraft, cruising at 38 thousand feet, had the autopilot suddenly trip off line, leaving the pilot[s] to hand fly the aircraft. This they failed to do. The aircraft went nose up and stalled. And stayed stalled, the pilots never pushed the stick forward to put the nose down, gain airspeed and fly out of the stall. The stall warning horn went off, but the aircrew failed to put the stick forward. The aircraft, stalled, fell from 38 thousand feet (seven miles high) and hit the sea.
This is really hard to believe, 'cause everyone knows about stalls, and everyone knows you push the stick forward to recover from a stall. There were three pilots on the flight deck, and not one of them came up with the right answer.
Contributing factor to the accident, the pitot tube iced up, which caused the indicated airspeed to drop to 60 knots. This is why the autopilot dropped off line, it is smart enough to know that the plane won't fly at 60 knots, something must be wrong, and it wanted the pilot to take over. Unfortunately the pilots could not fly the aircraft either.