A devastating fire blazed across the flight deck of doomed EgyptAir flight MS804 minutes before the aircraft plunged into the Mediterranean, according to the latest theories to explain the disaster.
Authorities had feared the plane was likely to have been the victim of a terrorist bomb attack when it went down on Thursday, killing all 66 people on board.
But now a more complex picture is emerging as experts sifted through new data yesterday, making an electronics fire a possible explanation.
The new information made terrorism seem 'less likely', although it has still not been ruled out.
Last night, authorities released an audio recording of the final words to Swiss air traffic control of pilot Mohamed Said Shoukair, who signed off about an hour into the flight: 'Thank you so much, good night.'
The audio indicates that all was routine as the plane checked in with air traffic controllers in Zurich, Switzerland, late Wednesday night, before being handed over to Italian air traffic controllers in Padua. The communication occurred around midnight local time, about two-and-a-half hours before Greek air traffic controllers in Athens lost contact.
The entirely unexceptional exchange suggests those on the plane had no notion at that time of what was to happen later.
Transmissions from the aircraft in the minutes before it was lost reveal that smoke was detected underneath the cockpit and in a toilet, according to messages transmitted to ground computers before the airliner plunged from the sky, killing ten crew and 56 passengers, including one Briton.
After meeting relatives of victims, French foreign minister Jean-Marc Ayrault said 'all theories are being examined and none is favoured'. But Simon Hradecky, editor and founder of the highly respected website Aviation Herald, said available data suggested an electrical fault on the jet was more likely than a terrorist attack.
Details of Flight 804's final moments emerged as human remains and personal belongings were recovered by search vessels from some of the victims who died when the Airbus A320 disappeared en route from Paris to Cairo. The Egyptian military released images of some items found, including life vests, parts of seats and objects clearly marked EgyptAir.
Debris was found 180 miles north of the port of Alexandria by the Egyptian navy. The spot is south of where the Airbus vanished from radar signals.
Meanwhile, an international air and sea search operation, involving the US and French navies, to locate the black box flight recorders intensified yesterday.
Because the search area covers 5,000 square miles – and some sections of the Mediterranean there are 10,000ft deep – it is feared that it could be weeks before the recorders are found.
Mr Hradecky speculated that the plane's oxygen supply could have been breached, causing the fire to spread more quickly, filling the cabin with smoke.
This, he said, is similar to what happened in 2011 when a fire started near the first officer's oxygen mask on an EgyptAir Boeing 777 during a fire at Cairo airport.
'If the oxygen bottle that feeds the oxygen masks of the pilots ruptures and feeds the fire, then we could have such a rapid development that the fire becomes catastrophic within three minutes.'
The Airbus A320 aircraft made a 90-degree turn left, and then dropped from 37,000ft to 15,000ft before swerving 360 degrees right. Contact was lost at 10,000ft.