Originally Posted by
Often1
The latter.
Take a simple example:
1. Purchase a ticket for $500.
2. Change the date and the flight now costs $400. AA issues a credit for $100 which can be used for a new ticket,
3. Change the date again and the flight now costs $500 again. You will need to pony up $100 in new funds for the fare difference.
In OP's case, the credit for the fare difference for the first change can't be used to pay the fare difference for the second change.
Correct me if I am wrong - so, in OP`s situation (or most situations), is it better to cancel the first ticket, and get the refund in one form of Flight Credit, not changing the dates? So the funds are in one form, and not in both, which are cannot be combined.
:-)