Originally Posted by
3Cforme
One can call 12 hours in advance of the desired flight to try a Same Day Flight Change for $50 according to the rules cited below:
http://www.aa.com/i18n/utility/sameDayTravel.jsp
Given that both Delta and JetBlue fly TPA-BOS non-stop, you really must have wanted to fly AA.
The Same Day Change is for the same city pair. Changing the city pair is not a "stand by" type thing... you will most likely be facing a fare change to route you over DFW.