To Daniel 11000 (and all French non-speakers)
Yesterday, I heard an interview of the BEA director on the french radio France Inter. Directly questioned by the journalist about the meaning of his wording "ligne de vol", he clearly explained that the choice of his words was probably not the best, but that he clearly ment "normal attitude" meaning with "wings level" with "no significant roll".
So to close the dabate, and with French my primary language, and having heard the explanation on France Inter directly from the guy, by "en ligne de vol" he definitely ment "normal attitude, with wings level"