The audio from a cockpit voice recorder revealed that one of the pilots was locked out of the cockpit before the crash in French Alps.

Germanwings plane fell 38,000 feet from the sky in just 10 minutes in the French Alps.

All the 150 people aboard were killed in the crash.

An investigating officer said that the pilot exited the cockpit and was unable to re-enter.

The officer said, “The guy outside is knocking lightly on the door and there is no answer, and then he hits the door stronger and no answer. There is never an answer and you can hear he is trying to smash the door down,”

He said that the reason why the pilot went of the cockpit is unclear.

“But what is sure is that at the very end of the flight, the other pilot is alone and does not open the door,” he added.

Air traffic controllers didn’t receive any emergency communication from the aircraft before the crash.

With no emergency call of anything unordinary the investigators are struggling to solve the mystery.

The descent was gradual indicating that the plane was in control of the pilots.

Remi Jouty, the head of the accident investigation bureau, or BEA said, “The descent is compatible with a plane controlled by pilots, it is also compatible with a plane controlled by automatic pilot.”

He added, “At this point, there is no explanation, one doesn’t imagine that the pilot consciously sends his plane into a mountain.”

The four possible causes of any crash are mechanical problems, human error, weather, criminal activity or any combination of these.

The investigators are still investigating and trying to solve the mystery that could have possibly taken the plane down.