The 121 victims of the Cyprus air disaster may have been dead before the plane smashed into a mountainside in Greece, officials have said.
Aviation experts and investigators are trying to unravel the sequence of events leading up to the crash.
All but 11 of the victims were Cypriot. Some 17 children are believed to have be among those who died.
Three days of mourning have been declared for the island's worst accident in decades.
Relatives of victims, who included 10 Greeks, have been arriving in Athens to identify the dead.
Flight 522 had been heading for Athens en-route to Prague when it lost contact with air traffic controllers, sparking a security alert before it crashed on Sunday afternoon.
The pilot of the Boeing 737, 50-year-old German Marten Hans Jurgen, was among the dead.
Experts looking into the cause of the crash believe a technical failure led either to a loss of cabin pressure or oxygen supply.
Greek Interior Minister Prokopis Pavlopoulos said: "It seems the deceased, in most cases, although not all, expired before the crash."
Coroner Philippos Koutsaftis told AFP news agency that the main hypothesis for cause of death was asphyxiation.
However, a defence ministry source quoted by Reuters said it appeared that the bodies had been frozen solid.
Greek police have arrested a man who claimed his cousin sent him a text message from the aircraft minutes before it crashed saying that everyone was frozen.
Relatives have vented fury on Helios Airways, accusing the company of allowing an unsafe aircraft to take to the skies - a charge the Cypriot carrier denies.
It has also denied a number of reports that it has grounded its entire fleet following the incident.
Company chairman Andreas Drakou said the crash was a terrible tragedy and apologised for the delay in announcing the names on the passenger list.
Both flight recorders have been recovered from the crash site but one of them is in a "very bad state", chief investigator Akrivos Tsolakis said.
'Out of control'
Crews of two Greek F16 fighter jets which were scrambled after contact with the airliner was lost, reported seeing the co-pilot slumped in the cabin.
They later saw two unidentified people trying to take control of the plane and could see oxygen masks hanging down in the cabin.
At least 17 children were believed to be among the dead
One theory is that sudden depressurisation in the cockpit overcame the pilots before they could take on oxygen and bring the aircraft to a lower, safer altitude.
"It was out of control," Greek air traffic controller Manolis Antoniadis was quoted by AFP as saying.
"There had to have been a fast and brutal problem to cause the death of the pilots in the cockpit."
He said the plane seemed to have got into difficulties 10 minutes after take-off.
In Greece, a special reception centre has been prepared for victims' relatives in the town of Marathon, not far from the crash site.
Orthodox priests and counsellors will be on hand to try to comfort the families.
Helios insists its plane was airworthy but Greek television has reported that the airline's fleet has had a history of technical faults.
On one recent flight from Warsaw to Larnaca, it said, passengers were taken off the plane suffering from respiratory problems.
"All our aircraft are checked very, very thoroughly according to international standards," said Vicky Xitas, Helios' commercial manager.
GREECE AIR DISASTER
1. 0900 [0700GMT]: Helios Airways Flight ZU522 leaves Larnaca bound for Prague via Athens
2. 0920 approx: Plane reaches cruising altitude of 35,000ft
3. 0937: Plane enters Greek airspace
4. 1007: Air traffic control unable to contact aircraft
5. 1030: Greek ATC issues "Renegade alert"
6. 1055: F16 fighter aircraft scramble
7. 1120: F16s intercept aircraft; pilots observed slumped over controls
8. 1205: Aircraft crashes near Grammatiko, 40km north of Athens
As an ex-aviator I must say what happened is a terrible event. People on board must have experienced low levels of oxygen first that would cause them to go unconscious even before the freezing cold. My deepest sympathy goes out to those who lost their loved ones in yesterday's tragedy.
Gurhan Kartal, Ankara, Turkey
I am a Cypriot citizen and since the terrible crash happened, the island of Venus is in a deep sympathy for those people who died and their families. Many people are still in a big shock. We (me and my boyfriend) knew 4 people on a plane: two couples around the age of 24-28. Two of them were the crew members, airhostesses. All I wish for them is to rest in peace.
Christiana Vasiliou, Nicosia Cyprus
Both my parents are from Cyprus, and I have many good friends living there too. This has truly hit me very hard as I feel, as small island, we are all like one family. My deepest sympathies to the people who lost their lives and their families. May God rest all of their souls.
Cleo Neophytou, Cambridge, UK
As a Turkish Cypriot, I would like to offer my deep and sincere condolences to the families and friends of those who tragically lost their lives in this terrible accident as well as to the entire Greek Cypriot population. This awful event has touched us all.
My sister lived in Cyprus for 4 years. Whilst visiting her I developed a love for the Cypriot people and their beautiful island. The loss of this plane with so many children on is a true tragedy. I have recently become a father for the first time and I only now understand how truly precious children are.
Ian Hepworth, Pickering, Yorkshire, England
My family live in Cyprus and my sister knows some of the people on that flight. With me being half Cypriot this terrible news has had a big impact on me. I would like to express my deepest sympathies to the people who lost their lives and their families god rest all of their souls.
Lambros Papantoniou, Grays, UK
I do not live near the crash scene, but two weeks ago - August 2nd - I survived the Air France flight 538 crash in Toronto. More and more I realise how truly lucky I am. My deepest sympathy goes out to the people who lost family and loved ones in this Greek air disaster.
Dennis Lewis, Sharjah, United Arab Emirates
In 1987 a (Monarch Airlines) 737 I was on (bound for Chania in Crete) lost cabin pressure/underwent sudden and total decompression somewhere over (mountainous) north Greece, and (to cut a longer story short) after a terrifying 'rapid descent' of about 30,000ft made an emergency landing at Athens airport. We passengers didn't know what was going on at the time - I for one thought we had all had our chips. This news made me wonder whether the 737 in question was the same one I was on all those years ago (surely they don't keep them in service that long?), or whether 737s have a particular problem with the mechanics of pressurisation. It also made me realise that my fears (and others) on that 737 bound for Crete were well-founded.
Eileen Hunt, Abingdon, Oxfordshire