Trainee Captain
Everyone is saying that it was the FO who had less then 50 hours on type. What I heard on this side of the pond is that it was a trainee captain with an instructor in the flight deck.
I hope these rumors are incorrect, as this situation makes it worse than a trainee FO (the reports say that PF joined company in 1994, so there is no way he was still an FO, may be change of fleet as a captain.)