French air crash investigators said Wednesday that Germanwings co-pilot Andreas Lubitz practiced a controlled descent on an earlier flight the day of the crash that killed himself and 149 people.

Authorities previously concluded that Lubitz deliberately crashed Germanwings Flight 9525 into the French Alps while flying from Barcelona, Spain to Dusseldorf, Germany on March 24. Investigators say Lubitz persuaded the flight's more experienced pilot to go to the bathroom before locking him out of the cockpit and sending the plane into a fatal dive. 

However, the French investigative agency BEA now says in an interim report that hours before the crash, Lubitz repeatedly sent the same Airbus A320 jet into a descent during the outbound flight from Dusseldorf to Barcelona before bringing it back to cruising altitude. The report added that the pilot appeared to have left the cockpit during the outbound flight was well.

Cockpit data shows that Lubitz put the plane into descent mode five times in a four and half-minute period during the Duesseldorf-to-Barcelona leg. The agency said it is continuing to look at the "systemic failings that may have led to this accident or similar events."

The investigators said their main focus is on "the current balance between medical confidentiality and flight safety" and the "compromises" made on security after the Sept. 11 attacks in the U.S., notably on cockpit door locking systems.

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Lufthansa spokesman Helmut Tolksdorf said by phone from Frankfurt that the airline had not yet had time to analyze the new details released by French authorities and planned no immediate comment. Lufthansa is the parent company of Germanwings.

Details of the earlier flight in the BEA's report were first described by the German tabloid Bild.

Investigators have said that Lubitz, 27, suffered from severe depression and had received, then torn up a doctor's note saying he was unfit to fly on the day of the crash. Computers removed from Lubitz's apartment in Dusseldorf showed that he had also researched methods of committing suicide in the days leading up to the crash. 

Last week, the Federal Aviation Administration released documents showing that officials questioned Lubitz's mental fitness to fly after he applied for a U.S. pilot's license in 2010.

As part of the application, he initially submitted a medical form to the FAA asserting that he had no mental disorders. He then resubmitted the form acknowledging he had been treated for severe depression from 2008 to 2009.

The FAA initially sent Lubitz a letter warning that his license application could be denied and giving him 30 days to provide a letter from his doctor describing his treatment and his current condition. The license was granted after his doctor described his treatment in letters and said he had recovered.

Fox News' Greg Palkot and the Associated Press contributed to this report.