The French authorities have confirmed that one of the black box flight recorders has been recovered from the site of Tuesday’s passenger plane crash in the French Alps.br br However it will be some time before the cause is known.br br A Germanwings Airbus A320 aircraft came down less than an hour into its journey from Barcelona to Dusseldorf with the loss of 150 lives.br br Euronews turned to aviation expert Bertrand Vilmer to try to shed light on the crash.br br Sophie Desjardin, euronews:br “Bertrand Vilmer, you are an aviation expert, and a former pilot. It is still early to draw conclusions on what really happened this morning above the Blanche Valley in the French Alps.br br We know some details: in particular the fact that the pilot did not send out a distress call but the plane seems to have fallen in stages. What do you think happened?”br br Bertrand Vilmer, aviation expert:br “There are two ways of making a distress call from a plane.