How much of a factor would fatigue play in this? I was struck by the fact that the German pilot and co-pilot left Frankfurt at 4am. Even if the flight had taken place at 12.30 as intended, that would still have been over eight hours since making an early start. By the time of the flight, they must surely have been more than a little tired. I'm surprised they weren't put up overnight in Perpignan before the flight. Might a bit of get-home-itis have set in?