Evidence has emerged that Andreas Lubitz, the co-pilot who last week brought down the Germanwings plane over the Alps, carefully planned his decision to lock the captain out of the cockpit and crash the aircraft.
Details from a transcript of the cockpit voice recorder from flight 4U9525, leaked to a German newspaper, appear to show that Lubitz repeatedly badgered Captain Patrick Sonderheimer to leave him alone on the flight deck.
Chillingly, when Capt Sonderheimer tried to brief Lubitz on plans for a routine landing in Dusseldorf, the First Officer replied: "Hopefully" and "We'll see".
In the closing moments of the recording, Capt Sonderheimer can be heard pleading with Lubitz to open the door before trying to break it down.
"For God's sake, open the door," he says, as the screams of passengers are heard behind him.
Lubitz flew the Airbus 320 into the French Alps last Tuesday, killing all 150 people on board.
The cockpit voice recorder, one of the plane's two boxes, was swiftly recovered.
Brice Robin, the French prosecutor in charge of the case, said last week that the recording indicated that Lubitz deliberately locked the captain out of the cockpit and set the plane in a fatal descent.
The German newspaper 'Bild am Sonntag' claimed it had obtained a transcript of the recording. Details from it appear to show that Lubitz's decision to lock the captain out was not a spontaneous act, as had been previously thought.
He did not simply take advantage when the captain slipped out, but actively encouraged him to leave the flight deck.
The recording, which is an hour-and-a-half long, begins with Capt Sonderheimer making a routine announcement to passengers, apologising for the late departure, according to 'Bild'. In the 20 minutes that follow, Capt Sonderheimer can be heard telling Lubitz that he hadn't had time to visit the toilet during their stopover in Barcelona.
It is at this point that Lubitz first suggests Capt Sonderheimer leave him alone in the cockpit, offering to take over.
Once the aircraft reaches its cruising height of 38,000ft, Capt Sonderheimer briefs Lubitz on a landing in Dusseldorf.
With the benefit of hindsight, the co-pilot's replies appear to show that he had already decided that flight would never make it to its destination.
But they probably did not ring any alarms for the captain at the time.
Once the briefing for the planned landing was complete, Lubitz again encouraged Capt Sonderheimer to go to the toilet and leave him alone in the cockpit.
"You can go now," he says. It is a full two minutes before Capt Sonderheimer takes him up on the offer.
"You can take over," he says.
He can be heard pushing back his seat, and then there is the sound of the cockpit door closing. It would not open again.
Almost immediately, the aircraft begins its descent. An automated alarm can be heard on the recording, announcing "sink rate" - a warning to pilots that the plane may be descending too fast.
Shortly afterwards, a bang can be heard from the cockpit door, followed by Capt Sonderheimer's voice. "For God's sake, open the door," he shouts, followed by the sound of passengers screaming behind him.
A few minutes later, there is the sound of loud metallic crashes. It is believed the captain tried to break the door down, possibly with a fire axe or a crowbar.
Another automated warning goes off, saying: "Terrain! Pull up! Pull up!"
Capt Sonderheimer shouts: "Open the damn door!"
The passengers can be heard screaming again. It is the last sound noted.
If these details are confirmed, they will be the first evidence that Lubitz planned the crash of flight 4U9525 and the deaths of everybody on board.
Sources inside the Dusseldorf police investigation have told 'Die Welt' newspaper they found evidence in Lubitz's Dusseldorf flat that he was suffering from serious mental health problems.
One said they found psychiatric drugs and other evidence that he was suffering from "severe burn-out syndrome".
He was also suffering from serious eyesight problems, and had already lost 30pc of his vision, 'Le Figaro' said.
It has been speculated that the fear that he would lose his career as a pilot because of his failing eyesight may have pushed Lubitz over the edge.
German media have speculated that the vision problems could have been psychosomatic, quoting studies that say that severe depression and failing eyesight are often linked.
DNA samples have been collected from 78 of the victims so far, and will be compared to DNA taken from family members, Mr Robin, the Marseille prosecutor, said.
Meanwhile, Andreas Lubitz was expecting a baby with his girlfriend, a German newspaper has claimed.
'Bild am Sonntag' reported that the woman, a teacher, had broken the news to her students within the past few weeks. It is unclear whether the news that he was about to become a father could have had any bearing on Lubitz's decision to crash the plane.