I haven't looked into it, but does anyone know off the top of their head whether those with WorldPerks or FlyingBlue accounts, as examples, have as many restrictions on which flights earn miles? I posted elsewhere that I have to use my WorldPerks account on my AMS-BUD flights and I have to be sure to pick the correct IAH-AMS flight for the reason the OP mentions. If I horded all my miles on my WorldPerks account, I wouldn't have either of those issues, but would I have issues getting credit for certain Continental flights, I wonder?