Acquaintances of Germanwings co-pilot Andreas Lubitz said he was happy and did not appear depressed.
French prosecutors believe the 28-year-old deliberately sent the jet crashing into the mountains to destroy the plane.
In Lubitz’s home town of Montabaur in western Germany, acquaintances said he showed no signs of depression when they saw him last autumn.
“He was happy he had the job with Germanwings and he was doing well,” said a member of a glider club, Peter Ruecker, who watched him learn to fly.
“He gave off a good feeling.”
Lubitz had obtained his glider pilot’s license as a teenager and was accepted as a Lufthansa pilot trainee after finishing a tough German college preparatory school, Mr Ruecker said.
He described Lubitz as a “rather quiet” but friendly young man.
Marseille prosecutor Brice Robin said the cockpit voice recorder gave information from the first 30 minutes of the flight.
For the first 20 minutes the two pilots talked in a normal fashion and were as courteous as two pilots would be.
He said the co-pilot’s responses, initially courteous, became “curt” when the captain began the mid-flight briefing on the planned landing.
'Several cries from captain'
The captain is then heard asking the co-pilot to take over and the sound of a chair being pushed back and a door being closed is heard.
It was assumed that the captain had gone to the toilet, leaving the co-pilot in charge of the plane, the prosecutor said.
Mr Robin went on: “We hear several cries from the captain asking to get in. Through the intercom system he identifies himself – but there is no answer. He knocks on the door and asks for it to be opened – but there is no answer.”
The Airbus A320, on a flight from Barcelona to Duesseldorf, began to descend from cruising altitude after losing radio contact with ground control and slammed into the remote mountain on Tuesday morning, killing all 150 people on board.
The captain had more than 6,000 hours of flying time and been a Germanwings pilot since May 2014, having previously flown for Lufthansa and Condor, Lufthansa said.