Originally Posted by ashill

Also, if you care about waived check bag fees and preferred seat assignments, it's certainly easier if your AA number is in the reservation. (It may or may not be possible to get preferred seat assignments and waived check bag fees with your AS number in the reservation.) Priority boarding is marginally easier with the AA number in the reservation because your boarding pass will say "Priority", but it's no problem to board early by flashing your AA elite card if they even bother to enforce priority boarding.