German prosecutors said that Germanwings co-pilot Andreas Lubitz hid illness from his employers and was supposed to be off sick on the day of the A320 crash.
The prosecutors found in the co-pilot's property in Düsseldorf, Germany, a torn-up sick note signing Lubitz off work on day of the French Alps crash. The "torn" illness certificate shows that Lubitz was receiving medical treatment.
They also said they could not find any suicide note or claim of responsibility in the apartment.
The development came after the SNPL, France's leading pilots union, filed a lawsuit over detailed reports in the media about the last 30 minutes of the doomed flight 9525.
French pilots are furious that key information about the final moments of the Germanwings A320 flight were leaked to the media before prosecutors were informed.
Guillaume Shmid, a representative of the union, said the lawsuit is over violating a French law on keeping information about investigations secret while they are ongoing, according to AP. The lawsuit does not name an alleged perpetrator.
The New York Times and AFP quoted senior military officials as saying that one of the two pilots of Airbus A320 left the cockpit and could not get back in at the time of the crash in the French Alps.
After the media leaks, French prosecutor Brice Robin confirmed that co-pilot Andreas Lubitz was alone inside the cockpit and deliberately manipulated the monitoring system to start descent of the plane and flew it into the mountains.
All 150 people aboard were killed.
Schmid said that pilots are saddened by the accident and understand the public's wish for immediate information, but condemned pressure on investigators and said they can mislead the public.