ATHENS - An airliner that crashed in Greece may have been a flying tomb when it plunged to Earth with some of the 121 people aboard already either dead or unconscious.
The crash, the worst air disaster in Greece, perplexed aviation experts, who are astounded by what appeared to have been a catastrophic failure of cabin pressure and/or oxygen supply at 35,000ft - nearly 10km up, higher than Mt Everest.
A top Greek Defence Ministry source said an autopsy on passengers "so far shows the bodies were frozen solid, including some whose skin was charred by flames from the crash".
Rescue workers recovered the pilot's body and found the plane's black box flight recorders, including the one that records pilot conversations. Investigators may focus on the last minutes of the Helios Airlines Boeing 737 flight which was declared "renegade" when it entered Greek air space and failed to make radio contact. Two F-16 Air Force jets were sent to investigate.
All 115 passengers and six crew died when the plane, with neither pilot in control, spiralled down in a death dive into a mountainous area about 40km north of Athens.
The plane was on a flight from Larnaca in Cyprus to Prague with a stop in Athens.
Cypriot Transport Minister Haris Thrassou strongly denied some media reports that there were 48 children among the dead.
"There were between 15 and 20 young people below the age of 20 on board the crashed plane," he said.
Airport officials said the flight left Cyprus at 9am (6pm NZ time) on Sunday and air traffic control lost contact at 10.30am. Greek Defence Ministry officials said 90 minutes elapsed between the alert first being raised and the plane crashing at 12.03pm.
Greek Government spokesman Theodore Roussopoulos said the F-16 pilots reported that with 737 pilots out of action there might have been a last-gasp effort by others on the plane to bring it back under control.
"The situation was characterised renegade, meaning the aircraft was not under the control of the pilots," Mr Roussopoulos said.
"At a later stage, the F-16s saw two individuals in the cockpit seemingly trying to regain control of the airplane. The F-16s also saw oxygen masks down when they got close to the aircraft. The aircraft was making continuous right-hand turns to show it had lost radio contact."
A passenger on the doomed plane said in a text message to his cousin in Athens: "The pilot has turned blue. Cousin farewell, we're freezing."
Reuters photographer Yannis Behrakis reported from the crash site that dozens of bodies were still strapped into their seats, some with the remnants of oxygen masks over their faces.
"Two charred bodies were still hugging each other," he said.
The Defence Ministry said it suspected the plane's oxygen supply or pressurisation system might have malfunctioned.
Loss of cabin pressure was identified as the probable cause of two similar but smaller-scale air crashes.
Pro-golfer Payne Stewart and five others were killed when their Learjet aircraft crashed in the United States in 1999 after flying for more than four hours without radio contact.
In 2000 a plane crashed in Australia after flying for more than an hour from 25,000ft up with no sign of life on board.
Experts said it was extremely rare for a plane to lose oxygen.
At Larnaca airport yesterday crew and passengers refused to board an aircraft belonging to Helios Airways, Cyprus News Agency reported.
About 100 passengers demanded to travel on planes of other airlines.
There are two types of decompression or loss of cabin pressure.
Creeping decompression: Caused by leaks from faulty window seals or small hull breaches. Gradual leaks provoke alarms, triggering oxygen masks and emergency measures to bring the aircraft down to breathable altitudes.
Rapid decompression: Cause could be sudden air conditioning failure and involves explosive noise. Leads to the expansion of gases within body cavities, loss of blood pressure, rupture of lung tissues and unconsciousness within 30 seconds.
Former BA captain Eric Moody said: " There's a big bang, and lots of white mist as the air inside disappears. You have to get an oxygen mask on as quickly as you can for an emergency descent."