Helios Airways Flight 522  was a Boeing 737-31S flight that crashed on 14 August 2005 at 12:04 EEST into a mountain north of Marathon  and Varnavas ,Greece. The leading explanation for the accident is that the cabin pressurisation did not operate and this condition was not recognised by the crew before they became disabled….

If you want read more about this accident  with evident aeromedical implications >> Helios Airways Flight 522