>>714749468I think he's confusing two incidents. The Gimli Glider worked out so well because the captain was a very experienced glider pilot and applied his knowledge of flying gliders to the situation in which his 767 was flying without power or hydraulics.
What the other anon said about the sim pilot being aboard was United Airlines 232 (DC-10) that crashed in Sioux Falls, Iowa. Without getting into too much detail, the aircraft had a catastrophic engine failure which lead to the loss of all flight controls.
While the Captain and First Officer dealt with the situation, a passenger aboard the aircraft made himself known to the crew to offer his assistance. That man was Dennis Fitch, a fellow United Airlines pilot and a flight instructor on the DC-10, as a stroke or fate or luck, Fitch had been running simulation flights in his own time in which he would simulate the loss of all flight controls and would attempt to steer the aircraft using only the engines.
It was a nasty crash, and over 100 people were killed but without the combined efforts of all 3 of them in the cockpit at that time, along with Fitch's knowledge on the matter, they'd probably have all fucking died.