I've searched and can't find the answer. I want to upgrade an existing trip (for someone else) with miles. I know there is a copay along with the miles (STX-TPA). I find that there is also a "service charge" when "ticketing via Reservations" of $20 if done 21 days in advance. My question is, can I do this via AA.com and avoid the charge? If so, how? Thanks.