(CNN) — Latest developments:
• 7:55 a.m.: The co-pilot of the doomed Germanwings flight “accelerated the descent” of the plane when he was alone in the cockpit, Marseille prosecutor Brice Robin said Thursday. That can only be done deliberately, he said.
• 7:55 a.m: The co-pilot was alive until impact, Robin said, citing the sound of steady breathing in the cockpit.
• 7:55 a.m: There was a “deliberate attempt to destroy the aircraft,” Robin said.
Audio from the mangled voice recorder of Germanwings Flight 9525 reveals a bizarre struggle on board: One of the pilots was locked out of the cockpit and was trying to get inside when the plane crashed, according to media reports.
“You can hear he is trying to smash the door down,” a senior military official involved in the investigation told The New York Times.
“We don’t know yet the reason why one of the guys went out. But what is sure is that at the very end of the flight, the other pilot is alone and does not open the door.”
Agence France-Presse also reported that a pilot was locked out, citing a source close to the investigation.
Lufthansa, the parent company of low-cost airline Germanwings, said it was looking into the reports.
“We have no information from the bodies investigating the incident that would corroborate the report in The New York Times,” spokesman Boris Ogursky said. “We will not participate in speculation, but we will follow up on the matter.”
The Times’ report is a “terribly shocking revelation,” CNN aviation analyst Peter Goelz said. But he and other experts cautioned that it’s still unclear what could have been going on inside the cockpit.
An array of theories
Possibilities range from a medical emergency to something more nefarious, such as a suicide mission, CNN aviation analysts said.
Reports of what happened have a “very sinister overtone” because of the way the Airbus A320 cockpit door locking system is set up, said Geoffrey Thomas, editor-in-chief of airlineratings.com.
The cockpit door has three positions, he said, citing A320 captains and the aircraft manual — unlocked, normal and locked.
The door would usually be in the “normal” position, but if the Times report is true, it would appear that after one of the pilots left the cockpit, it was switched to the “locked” position. This prevents the other pilot from using a keypad and emergency code to get in from the outside, he said.
The chances of this happening accidentally if the pilot became incapacitated, at the same time as him knocking the side stick to put the plane into a dive, would appear to be “beyond the realms of mathematical possibility,” Thomas said.
Officials previously said they hadn’t ruled out terrorism, but that it seems unlikely.
French authorities have disclosed few details about what the recording actually contained.
“It is too early to draw conclusions to what happened,” said Remi Jouty, head of the BEA, the French aviation investigative arm leading the probe. “There is going to be detailed work performed on that audio file to understand and interpret the sounds and the voices that can be heard.”
Waber Joerg, a spokesman for Lufthansa, said it’s not unusual for one pilot to be in the cockpit.
“The authorities and regulations stipulate that a pilot can be in the cockpit alone,” he said. “It is recommended that this time be kept to a minimum. We comply with all German and European aviation authorities.”
Second ‘black box’ still lost
Finding the plane’s second “black box” will also be critical to understanding the mystery of what went on inside the jet.
That box, the flight data recorder, hasn’t been found yet, but Lufthansa CEO Carsten Spohr said Wednesday that there’s a high probability it will be.
More answers may also come in news conferences scheduled for later Thursday by the Marseille prosecutor and senior executives from Germanwings and Lufthansa.
The Germanwings media office told CNN the captain of Flight 9525 had more than 6,000 hours of flight time. He has been with Germanwings since May 2014 and had worked with Lufthansa and Condor before then.
The co-pilot has been with Germanwings since September 2013 and had completed 630 hours of flight time, the media office said. The co-pilot had trained at the Lufthansa flight training center in Bremen, Germany.
A dangerous search
Relatives and friends of the victims embarked on an emotional trip Thursday: traveling close to the mountainous spot where their loved ones perished.
Special Lufthansa flights from Germany and Spain are taking relatives and friends of the victims to southern France. The airline has offered to take them as close to the crash site as possible “within the safety parameters of the investigation,” Lufthansa said in a statement.
They are first expected to stop in the town of Le Vernet for a “moment of reverence,” Seyne-les-Alpes Mayor Francis Hermitte said.
They will then carry on to the village of Seyne-les-Alpes, which has become a staging post for the recovery operation. A further ceremony is expected there, Hermitte said.
He said he anticipated 200 to 300 people would come to the area Thursday, not just relatives of the victims but also people close to the families.
Most are not expected to stay overnight, he said. But in case they do, he said, local residents have spontaneously offered accommodations for them to stay.
While some human remains have been recovered from the crash scene, many have not. And the task is treacherous for search crews.
The plane crashed in the French Alps, where slopes are steep and the weather has been icy.
The only way workers could get to the site was to drop from helicopters. Jouty, the head of the French team leading the investigation, said they had to be together for safety.
Victims from 18 countries
The doomed flight was traveling from Barcelona, Spain, to Dusseldorf, Germany, when it crashed Tuesday.
Germanwings said the plane reached its cruising altitude of 38,000 feet, and then dropped for about eight minutes. The plane lost contact with French radar at a height of about 6,000 feet. Then it crashed.
There were 150 people from 18 countries on board.
Teams have begun the daunting task of identifying the victims’ bodies but caution that it could take time to complete.
Clues in the debris
Investigators are still trying to piece together what caused the crash.
Jouty said the debris suggests the plane hit the ground and then broke apart, instead of exploding in flight.
Radar followed the plane “virtually to the point of impact,” Jouty said.
FBI agents based in France, Germany and Spain are looking through intelligence sources and cross-referencing the passenger manifest, two senior law enforcement officials said.
So far, one official said, the search hasn’t turned up anything that “stands out” or anything linking the passengers to criminal activity.
CNN’s Frederik Pleitgen, Nic Robertson, Pierre Meilhan, Richard Quest, Hala Gorani, Stephanie Halasz, Khushbu Shah, Bharati Naik, Ingrid Formanek, Sandrine Amiel and Erin McLaughlin contributed to this report.
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