Hi. We've only dared two summer return trips , in early Juy (2008, 2007), on NW AMS-BDL (Hartford), and found a fair amount of space both times. I know that's not what you asked specifically, but there you have it. Good luck, and let us know how you do! See posts elsewhere for pass travel out of CDG (search for CDG).
OK. now I re-read your pos, you're just asking about travel INSIDE europe..well anyway...