The co-pilot who is believed to have deliberately crashed a Germanwings jet in the French Alps may have "rehearsed" steering the plane into a rapid descent on an earlier flight, German daily Bild reported.
Quoting sources close to the French investigating authorities, the newspaper said that the co-pilot, 27-year-old Andreas Lubitz, appeared to have tried out a "controlled, minute-long descent for which there was no aeronautical reason" on the earlier outbound flight from Dusseldorf to Barcelona.
Investigators had discovered this after a close evaluation of the jet's black-box flight recorder, Bild said.
The French authorities are scheduled to publish an interim report on their investigation into the crash later on Wednesday, but declined to comment on its contents or on the Bild report.
The Germanwings Airbus 320 was en route from Barcelona to Duesseldorf when it crashed in the French Alps on March 24, killing all 150 people on board.
French investigators believe that Lubitz, who had been diagnosed as suicidal in the past, deliberately brought the plane down.
Doctors had recently found no sign that he intended to hurt himself or others, but he was receiving treatment from neurologists and psychiatrists who had signed him off sick from work a number of times, including on the day of the crash.
Police found torn-up sick notes during a search of his apartment after the crash.
Lufthansa, which owns Germanwings, declined to comment on the Bild report, pointing to the ongoing investigation.