Be sure to research BA fuel surcharges. I did redeem American miles on BA and dealt with the fuel surcharges (and seat selection fees) to get my first 747 ride (and secured the upper deck), which was worth it to me for that reason, at least at the time, but if you don’t care about those things, do know what you’re looking at for taxes and surcharges as it may make the mileage redemption not worth it to you.