Originally Posted by
Often1
Although it's not authorized, you can sometimes SDC between local airports such as MIA & FLL or LGA & JFK. But, what you are seeking is a change in your itinerary. Presuming that you are on a restricted ticket, that's $200 + fare difference. Note that the fare difference might be in your favor and that might mean that you come out OK even with the $200.
Why not check that out first?
Some airlines, such as UA and US, no longer allow you to take the $200 change fee out of the fare difference if the new fare is lower than the old fare - that is, you have to pay the $200 no matter what. If the new fare is lower than the old fare, you pay $200 and lose the difference.