Andreas Lubitz, the co-pilot who appears to have deliberately crashed his aircraft into the French Alps last week, had informed Lufthansa in 2009 of a "serious depressive episode," the German airline said in a statement.

Lufthansa says a note about a "previous depressive episode" was found in email Lubitz apparently sent to the Lufthansa flight school when he resumed his training after a months-long interruption.

The airline said Tuesday it provided the documents to prosecutors, who are investigating the crash of Germanwings Flight 4U 9525 on March 24. The crash killed Lubitz and 149 others who were traveling from Barcelona, Spain, to Duesseldorf, Germany. Lufthansa is the parent company of Germanwings, a budget carrier.

Lufthansa's announcement is the first acknowledgment by the airline that it knew of Lubitz's health condition. Lubitz, the airline's CEO Carlten Spohr said last week, joined Germanwings in 2013, directly after training.

Prosecutors in Duesseldorf previously said Lubitz appears to have concealed a medical condition from his employers. O n Monday, a prosecutor said the co-pilot received treatment for suicidal tendencies several years before he became a pilot.

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