A senior military official involved in the investigation described “very smooth, very cool” conversation between the pilots during the early part of the flight from Barcelona to Düsseldorf. Then the audio indicated that one of the pilots left the cockpit and could not re-enter.

“The guy outside is knocking lightly on the door and there is no answer,” the investigator said. “And then he hits the door stronger and no answer. There is never an answer.”

He said, “You can hear he is trying to smash the door down.”

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