ATHENS, Greece, Aug. 15 (UPI) -- The investigation into the crash of a Boeing 737 on a mountain near Athens centers on what happened to the oxygen system.
Two Greek F-16s were dispatched when air traffic controllers lost contact with Helios Airways Flight 522 as it entered Greek airspace. The military pilots reported seeing the jetliner's co-pilot slumped over the controls, the International Herald-Tribune reported.
The plane descended, apparently on autopilot, until it crashed into a mountain north of Athens, killing all 121 people aboard.
Greek authorities have recovered both flight data recorders but investigators say the voice recorder suffered considerable damage.
Flight 522 was bound for Prague with a scheduled stop in Athens and crashed at 12:20 p.m. Sunday.
Local media was reporting many victims froze to death before the crash, which is tentatively blamed on a cabin decompression, which knocked out both pilots from lack of oxygen, the BBC reported.
The Greek government said there was no reason to suspect terrorism.
Cyprus has declared three days of public mourning for the worst accident to hit the island in decades.