Germanwings Co-Pilot Practiced Descent Before Crash

The Germanwings co-pilot that prosecutors say crashed Flight 9525 into the French Alps attempted a controlled descent on an earlier flight that day, according to a 30-page report by France's BEA investigation agency.

Investigators said that more than once, co-pilot Andreas Lubitz put the A320 jet into a descent, only to bring it back up again. It happened on a March 25 flight from Dusseldorf to Barcelona when the pilot was out of the cockpit.

"The process of going up and down with the selected altitude is not normal - but I can't tell you what was going on in his head," said Antoine Amar, a top official in France's main pilots union SNPL and an Air France pilot who has flown the A320.

Later that day, on the return flight, prosecutors say Lubitz intentionally crashed the jet into the Alps, killing all 150 passengers on board. His motives remain unclear.