French crash investigation agency (BEA) released a report on Wednesday about the crash of Germanwings Flight 4525.
The Airbus 320 crashed into the French Alps on its way back to Germany on March 24. Black box records suggested that Lubitz locked the cockpit door when the head pilot was out and killed all of the 150 passengers on board.
BEA wrote in the interim report that co-pilot Andrea Lubitz crashed the jet into the mountain.
French investigators pointed out that on March 24, the co-pilot carried out a controlled descent in a previous flight to Barcelona.
The report mentioned that Lubitz had a "controlled, minute-long descent for which there was no aeronautical reason."
Investigators believed that the co-pilot had a depressive background in the past. German prosecutors also noted that Lubitz researched suicide methods over a number of months.
The agency stated that they are still searching for the reason for the co-pilot’s deliberate crash into the French Alps.