Five years before he allegedly deliberately crashed an airplane into the French Alps, killing all 150 people aboard, Germanwings co-pilot Andreas Lubitz was questioned over his mental health by the US Federal Aviation Administration, according to documents revealed Thursday.

In response to a Freedom of Information Act request, the FAA published documents online pertaining to Lubitz's time in flight school in Phoenix, Arizona, while working toward his US pilot's license in 2010.

The records show that Lubitz applied for the license while employed by Lufthansa, the parent company of Germanwings. He initially attached a medical form to the application which indicated he had no mental health issues, before resubmitting the document, this time admitting he had been treated for severe depression between 2008 and 2009.

The FAA responded by warning Lubitz that his application could be denied on these grounds, and gave the young co-pilot 30 days to provide a doctor's letter detailing his treatment and current mental condition. The doctor, whose name was blacked out by the FAA, said Lubitz had suffered a suicidal episode because he was unable to cope with "modified living conditions" and had been treated with two different kinds of antidepressant drugs.

Along with therapy, the drugs enabled Lubitz to "develop sufficient resources for getting on with similar situations in the future," the doctor wrote.

Authorities have said they believe Lubitz intentionally crashed the Germanwings Flight 9525 from Barcelona to Düsseldorf on March 24 after black box recordings indicated Lubitz locked the pilot out of the cockpit and refused to let him back in.

es/jil (AP, dpa)