The Greek report blamed mistakes during technical checks on the ground and failure by pilots to pick up on compression warnings during flight for the Cypriot Helios Airways crash in August 2005.
The pilots did not realise that the cabin’s pressurisation selector had been left in manual position during an inspection before take-off from Larnaca in Cyprus.
The compression system regulates the oxygen supply inside the aircraft, which decreased as it gained altitude causing the passengers and crew to lose consciousness.
The aeroplane flew on autopilot for two hours, with its pilots slumped over the controls, before it ran out of fuel and crashed into a Greek hillside.
The pilots of two Greek air force fighter planes, which were scrambled when ground controllers lost radio contact with the passenger jet, reported seeing a flight attendant – the only person still conscious – struggling with the controls before the flight crashed.
Before losing contact, the pilot had reported a problem with the Boeing 737’s air conditioning system.
The airline, Cypriot regulatory authorities and Boeing were all criticised by the Greek investigators.
The report said that the plane’s manufacturer had taken “ineffective” measures in response to previous pressurisation incidents on that particular type of aircraft.
Helios was found to have “deficiencies” in its organisation, and the Cypriot regulatory authority was accused of “inadequate execution of its safety oversight responsibilities”.