The Germanwings co-pilot appeared to want to "destroy the plane", a French prosecutor has said.
Marseille prosecutor Brice Robin said the co-pilot was alone at the controls and “intentionally” sent the plane into the doomed descent.
He said pounding could be heard on the door during the final minutes before the crash as alarms sounded.
The co-pilot, identified as 28-year-old Andreas Lubitz, “voluntarily” refused to open the door and his breathing was normal throughout the final minutes of the flight, he said.
Asked about Mr Lubitz's ethnicity, Mr Robin said: “He was a German national and I don't know his ethnic background.
“He is not listed as a terrorist, if that is what you are insinuating.”
Pressed on the co-pilot’s religion, he said: “I don’t think this is where this lies. I don’t think we will get any answers there.”
Mr Robin said black box recordings showed that Mr Lubitz “was breathing normally, it wasn’t the breathing of someone who was struggling”.
Speaking about whether the passengers realised what was happening, Mr Robin said: “I think the victims only realised at the last moment because on the recording we only hear the screams on the last moments of the recording.”
He added: “I believe that we owe the families the transparency of what the investigation is pointing to and what is going on, we owe it to them to tell them what happened.
“The families have been informed of everything I just told you.”
#BREAKING Co-pilot was German, no terrorist profile: prosecutor
— AFP News Agency (@AFP) March 26, 2015
He said information has been pulled from the black box cockpit voice recorder but the co-pilot did not say a word once the captain left the cockpit.
“It was absolute silence in the cockpit,” he said.
Mr Robin said the plane may have glided before the moment of impact.
He said there was no distress signal, no Mayday and no answer despite numerous calls to the plane.
Mr Robin said: “The interpretation of the cockpit voice recorder evidence is that the co-pilot voluntarily refused to open the cockpit door to the captain.”