The co-pilot of the flight that crashed into the French Alps last week had told Lufthansa's flight school in 2009 that he had suffered from a "previous episode of severe depression," the airline said in a statement Tuesday.
The co-pilot, Andreas Lubitz, later completed his training and received a medical certificate confirming his ability to fly, Lufthansa said. Lufthansa is the parent company of the budget airline Germanwings, whose Flight 9525 was destroyed after Lubitz allegedly rammed the plane into a mountainside one week ago.
Lufthansa says Lubitz wrote to the company's pilot training school in 2009 about a previous episode of severe depression and submitted medical documents connected to the condition before resuming his flight training.
Lufthansa had previously said that Lubitz's training, which took place in Phoenix and Bremen, had been interrupted for a period of several months six years ago.
The airline said in its statement that it had provided the documents to prosecutors investigating the case.
Questions have been raised about what the airline knew about Lubitz's condition before the crash, which killed all 150 people on board.
The Germanwings Airbus A320 was traveling between Barcelona and Düsseldorf when it is believed that Lubitz deliberately descended the plane, based on evidence from the black box audio recordings.
Additional information from The Associated Press.