From reader Isaac Lubow:
In 2008 a Learjet operated by Kalitta Air was en route from Manassas, Va., to Ypsilanti, Mich., when the air traffic controller noted that the pilot’s microphone button was being pressed continuously. When he contacted the plane, the pilot told him in slow, slurred words, over the sound of audible alarms, that he was unable to maintain altitude, speed, or heading but that everything else was “A-OK.”
Euphoria is a sign of hypoxia. With the help of the pilot of a nearby aircraft, the controllers were able to understand that the Learjet had become depressurized. It turned out that the first officer had been completely unconscious, and his flailing arm had both disengaged the autopilot and keyed the microphone. The open microphone had alerted the controllers, and the need to hand-fly the plane had kept the pilot conscious and able to respond to their commands.
The pilot managed to descend from 32,000 feet to 11,000, where the crew recovered, and the plane landed safely at Detroit’s Willow Run Airport. Controllers Jay McCombs and Stephanie Bevins were awarded the Archie League Medal of Safety, and the episode is now used as a classroom teaching aid at the Civil Aerospace Medical Institute in Oklahoma City.
(From Fear of Landing. Thanks, Isaac.)