A rescue worker climbs past debris at the plane crash site near Seyne-les-Alpes, France. Photo / AP
A rescue worker climbs past debris at the plane crash site near Seyne-les-Alpes, France. Photo / AP
One of the two pilots on the doomed Germanwings flight was apparently locked out of the cockpit before the plane crashed in the French Alps.
Cockpit recordings recovered from the site of the crash that killed all 150 people on board indicated one of the seats was pushed back and the door opened and closed.
Knocking can then be heard, said a source close to the investigation, adding "there was no more conversation from that point until the crash".
Rescue workers at the plane crash site near Seyne-les-Alpes, France. Photo / AP
The source said an alarm indicating the proximity to the ground could be heard before Germanwings flight 4U9525 from Barcelona to Duesseldorf crashed in remote terrain after an unexplained eight-minute descent in mid-flight.
No distress signal was sent from the Airbus A320 and the crew failed to respond to ground control's desperate attempts to make contact.
The cockpit recording of Tuesday's flight showed the pilots speaking normally in German at the start of the flight, the source said, adding that it could not be determined if it was the captain or the first officer who left the cockpit.
The New York Times cited a senior military official involved in the investigation as saying the black box data indicated one pilot was locked out and tried unsuccessfully to smash his way back in.
Photos of the mangled black box retrieved at the site showed its metal casing torn and twisted. The casing of a second black box, the flight data recorder, has been found but not the device itself.
Investigators have said the plane was still flying when it smashed into the remote mountainside, with the force of the impact leaving only small pieces of debris scattered over a wide area.
A mountain guide who got near the crash site said he was unable to make out recognisable body parts.
"It's incredible. An Airbus is enormous. When you arrive and there's nothing there ... it's very shocking," said the guide, who did not wish to be identified.
A French army helicopter heads to the Germanwings flight crash site. Photo / AP
The crash site is at about 1500 metres altitude and accessible only by helicopter or an arduous hike on foot.
Arrangements were being made for the families of the victims, at least 51 of whom were Spaniards and at least 72 Germans, to gather near the crash site on Thursday.
Lufthansa, which owns popular low-cost operator Germanwings, announced it would lay on two flights to take the victims' loved ones from Barcelona and Duesseldorf to the southern French city of Marseille.
Helicopters began winching the remains of victims to Seyne-les-Alpes on Wednesday.
Interpol said it had dispatched a team of victim identification experts to the site.
Authorities who had the gruesome task of sifting through the debris called off the search at nightfall on Wednesday. They will resume at dawn.
Weather does not appear to be a factor in the crash and Germanwings had an unblemished safety record.
French President Francois Hollande and German Chancellor Angela Merkel flew over the site to see the devastation on Wednesday. Spain's Prime Minister Mariano Rajoy also visited a crisis centre near the scene.
"My deepest sympathies with the families and all my thanks for the friendship of the people of this region and in France," Merkel wrote in a book of condolence.
A rescue worker climbs past debris at the plane crash site near Seyne-les-Alpes, France. Photo / AP
The plane was carrying six crew and 144 passengers, including 16 German teenagers returning home from a school trip.
Bereaved pupils from their high school in the small German town of Haltern wept and hugged near a makeshift memorial of candles as they shared the pain of losing their friends.
"Yesterday we were many, today we are alone," read a hand-painted sign at the school, decorated with 16 crosses.
Those killed - most of them about 15 years old - had reportedly won the trip in a lottery of their classmates.
