If anyone would like to listen to the ATC radio: https://www.youtube.com/watch?v=ZW-ETmZU0u8
> Ladies and gentlemen, this is your captain speaking. We have a small problem. All four engines have stopped. We are doing our damnedest to get them going again. I trust you are not in too much distress.
"Unable... to control... altitude" "Unable... to control... airspeed" "Unable... to control... heading" "Other than that, everything A-OK!"
Guy landed safely after ATC realized it was hypoxia and ordered the flight to descend.
EDIT: link https://fearoflanding.com/accidents/accident-reports/hypoxia...
And the recent case of Captain Maggie: https://youtu.be/B229-KLudTo
The pilot sounds calmer than the ATC. Former fighter pilot.