It depends on the fare basis, but IME most I fares are non-refundable. Fare basis varies based on originating and destination cities, dates, day of week traveling, how far in advance fare is purchased, etc. Below are fare basis for DCA-LHR I fares. The more expensive the ticket, generally the more likelihood that it is refundable. The fare basis shown below are sorted by their respective prices (low to high, but not shown). So for example the second to last fare basis listed below is for a round trip ticket that costs $4800 USD and is refundable but incurs a fee of $275 to do so:

To find out whether your fare is refundable, and if so if there is a fee incurred it is probably easiest to call AA. Either that or go to the refund page and find your fare rules. Somewhere on FT there are instructions on how to find out from the refunds page or perhaps someone else can help with instructions. On the rare occasion I neglected to check my fare rules, I call AA for info.