FRANKFURT--The co-pilot allegedly responsible for last week's Germanwings plane crash informed his flight training school he had suffered a "previous episode of severe depression," airline Deutsche Lufthansa AG (DLAKY, LHA.XE) said Tuesday after handing further documents over to Duesseldorf prosecutors.

The co-pilot, Andreas Lubitz, told the school in 2009 of the episode in email correspondence before resuming flight training, which he had interrupted for several months, Lufthansa said. He later received a medical certificate confirming his fitness to fly.

Prosecutors allege Mr. Lubitz deliberately slammed the plane into the French Alps last Tuesday after locking the pilot out of the cockpit, killing all 150 people aboard.

"To ensure a swift and seamless clarification, Lufthansa--after further internal investigations--has submitted additional documents to the Duesseldorf Public Prosecutor, particularly training and medical documents," the airline said.

Lufthansa, which operates Germanwings, said it continues to support authorities in charge of the probe, but wouldn't comment further so as not to interfere with the investigation.

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