Lufthansa knew that the co-pilot of the passenger plane that crashed in the French Alps last week had suffered from an episode of “severe depression” before he finished his flight training with the German airline.

The airline said Tuesday that it has found emails that Andreas Lubitz sent to the Lufthansa flight school in 2009 when he resumed his training in Bremen after an interruption of several months.

In them, he informed the school that he had suffered a “previous episode of severe depression,” which had since subsided.

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