Hypoxia on a flight to Athens
Open event
Helios Airways Flight 522, a Boeing 737-300 flying from Larnaca to Athens and Prague on 14 August 2005, never pressurised because a selector had been left in manual after overnight maintenance, and the pilots were overcome by hypoxia as the aircraft climbed on autopilot. It flew on unresponsive for almost three hours, circling near Athens until its fuel ran out, and crashed into hills near Grammatiko, killing all 121 people on board.
3 video perspectives
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50:03
This Mayday episode follows Greek investigators as they work out why a Helios Airways 737 flew silently for almost three hours before crashing near Athens in August 2005, killing all 121 on board.
Published 14 May 2021
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1:10:31
Airline captain Petter Hörnfeldt traces Helios Flight 522 from the airline's audit failures and the 737's history of pressurisation faults to the overnight test that left the selector in manual.
Published 16 May 2026
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18:21
Helios Airways Flight 522 took off from Larnaca in August 2005 with its pressurisation selector left in manual after night maintenance, and its pilots mistook the cabin altitude horn for a takeoff…
Published 24 Oct 2026