The co-pilot of the Germanwings plane that crashed in the French Alps in March appears to have practised a rapid descent on a previous flight, a report by French investigators says.
The report said Andreas Lubitz repeatedly set the same plane for an unauthorised descent earlier that day.
Lubitz is suspected of deliberately crashing the Airbus 320, killing all 150 people on board.
He had locked the flight captain out of the cockpit.
Lubitz appears to have practised programming a rapid descent on the outbound leg of the flight - from Duesseldorf to Barcelona on 24 March - the preliminary report by accident investigation agency BEA said.
It added that on several occasions - again with the captain out of the cockpit - the altitude dial was set to 100ft (30m), the lowest possible reading, despite instructions by air traffic control in Bordeaux to set it to 35,000ft and then 21,000ft.
It was also reset on one occasion to 49,000ft, the maximum altitude.
The changes apparently happened over a five-minute period at about 07:30 starting 30 seconds after the captain left the cockpit.