Welcome to FT, brook.

I'm sure someone with more BA experience will come along and offer more insight.

In the meantime, I will say that you usually can earn miles on one partner when flying another. Just enter the account # you want to earn on when you book the ticket. If the web site does not accept the #, you can call and have it added to your reservation.

Moving your existing AA miles to BA is a bit more difficult, and you will likely lose miles in the process. InsideFlyer offers a mileage converter to help you figure out ways to do this. Depending on how many miles you have, it might be better to 'top off' the AAdvantage account to redeem for an AAward or upgrade.