Autopilot in the Dark: The 2005 Helios Flight 522 Crash and Its Regulatory Aftermath

A Helios Airways Boeing 737 depressurized after a ground crew left the cabin pressurization on manual, causing hypoxia that left everyone aboard unconscious while the autopilot kept the plane circling toward Athens for over an hour. A lone flight attendant with a portable oxygen supply stayed conscious long enough to signal F-16s and attempt to wake the pilots, but the engines failed and the aircraft crashed near Grammatiko, killing all 121 on board. Investigations led to regulatory changes including cockpit warning lights distinguishing takeoff vs. pressurization alerts and expanded hypoxia training to prevent a repeat.