Thanks for your comments !
Sorry not to have any idea of flight nr. ! But ... Regarding its direction (south to south west), it can be a plane going to Toulouse, or Spain (Italy ?)
Regarding its altitude, it can't come from Paris CDG. It could come from Beauvais or Lille airport, but flight schedules are not compliant (or charter ?)
It could also come from Bruxelles but it seems to be quite low...
Really, I can't go further ; )
Rendez-vous next friday, hoping it is a regular flight with no delay !