Germanwings crash: What we know about the final moments before the plane hit the ground

The co-pilot of the Germanwings airplane locked himself inside the cockpit and intentionally made the plane rapidly descend in order to destroy it, French investigators revealed today.

Investigators say they have no reason to believe the incident was a terrorist act. But they are at a loss to explain why co-pilot Andreas Lubitz, 28, decided to take his own life and that of 149 other passengers and crew on-board Airbus A320 by crashing it into an Alpine ravine on Tuesday.

Here is what we do know about the aircraft’s final moments according to Marseille prosecutor Brice Robin.

Both captain and co-pilot were behaving normally before the crash

The pair engaged in “normal” conversation for the first 20 minutes of the flight heading from Barcelona to Dusseldorf. But Lubitz's replies became “laconic” as they started readying what would have been the normal descent to the German airport.

“His responses become very brief. There is no proper exchange as such,” Robin said.

The captain left the co-pilot alone

The captain asked Lubitz to take over, and left the cockpit for around ten minutes, probably to use the bathroom.

Lubitz locked himself in the cockpit

Investigators said Lubitz purposefully locked the captain out and himself inside the cockpit, because this can only be done manually.

By doing so, he overrode the A320 Airbus’ safety mechanism which allows emergency entry into the cockpit.

The descent begins

When Lubitz was left alone, he used the flight monitoring system to lower the plane.

The captain banged at the cockpit door

The black box recorder revealed that someone, likely the pilot, pounded on the cockpit door after Lubitz locked the door.

There was no distress call

What concerned investigators before the black box was found was that no distress was sent out from the cockpit when the plane began plummeting. Pleas for response from the control tower were also ignored by Lubitz, and of course the captain who was locked outside at the time.

Lubitz remained silent during the descent

His breathing was calm as the plane’s instrument alarms sounded and the captain pounded on the cockpit door.

"You don't get the impression that there was any particular panic, because the breathing is always the same. The breathing is not panting. It's a classic, human breathing," Robin said.

The captain is also ignored when he identifies himself through the intercom system.

Screaming could be heard as the plane neared impact

The 144 passengers only realised at the last moment what was happening, and screams were only heard in the last moments of the recording, before the impact.

"The victims realised just at the last moment," Robin said. "We can hear them screaming. Death was instant. It hit the mountain at 700km (430mph) an hour."

The plane crashes

The black box recorder picked up the sound of pounding during the final minutes as alarms sounded. Finally the sound of an impact is heard.

Additional reporting by PA