article_snippet.sent: One of the strongest pieces of evidence to emerge from the crash so far comes from the cockpit voice recorder.
article_snippet.sent: The sounds recorded on the recorder, known as a "black box," firms up a theory by investigators that a pilot locked the captain out of the cockpit and then crashed the plane.
article_snippet.sent: The audio from the plane's cockpit voice recorder has not been released, but the German newspaper Bild published Sunday what the German newspaper Bild claims is a summary of the transcript from the recording.
article_snippet.sent: CNN cannot independently verify the information, which Bild says is based on 1.5 hours of audio that was on the cockpit voice recorder.
article_snippet.sent: Cockpit recordings are some of the most sensitive and closely held parts of aviation crash investigations.
article_snippet.sent: Cockpit recordings're never officially released, according to CNN aviation reporter Richard Quest.
article_snippet.sent: CNN aviation reporter Richard Quest called it "unbelievable" that the black box audio would be leaked in this manner.
article_snippet.sent: Communications between air traffic control and a plane's cockpit can be downloaded privately, but that's less common in Europe than it is in the United States.
article_snippet.sent: An edited and redacted version of the transcript is usually published in part of a final report on an incident.
article_snippet.sent: Although search teams have recovered the cockpit voice recorder, the flight data recorder remains missing.
article_snippet.sent: That device could reveal crucial details about what happened during the final moments of the flight.