Prosecutors: Germanwings co-pilot was treated years ago for suicidal tendencies
There was reportedly "no evidence" that 27-year-old Andreas Lubitz told anyone what he was planning, and prosecutors said they didn't find any indications of his motive.
All 150 people on board the Germanwings plane died in the crash.
Lubitz reportedly received psychotherapy "with a note about suicidal tendencies" before he became a pilot.
Lubitz reportedly hid his illness from his employer before he took down the Germanwings plane. Investigators found a doctor's note at Lubitz's home last week declaring him unfit for work, but Lufthansa, which owns Germanwings, said the note had not been submitted to the company.
German tabloid Bild reported last week that Lubitz suffered a "severe depressive episode" years ago.
Lubitz might also have been close to losing his pilot job - he was reportedly being treated for vision problems that could have affected his ability to fly.
French authorities say Lubitz input the command to start the plane's descent after the captain left the cockpit to go to the bathroom. The captain can be heard on the cockpit voice recorder trying to break down the door before the plane crashed, but Lubitz would not let him back in.