Helios Airways Flight 522 was a scheduled passenger flight from Larnaca, Cyprus to Prague, Czech Republic, with a stopover in Athens, Greece, that crashed on 14 August 2005, killing all 121 passengers and crew on board. A loss of cabin pressurization incapacitated the crew, leaving the aircraft flying on autopilot until it ran out of fuel, and crashed near Grammatiko, Greece. It was the deadliest aviation accident in Greek history.