Originally Posted by
Often1
The problem for OP is that he then has to go to whichever WAS airport it is, find an agent, see if he can change the flight (it's not really an SDC, but an agent making the change & waiving the fee) and then either going home or sitting around IAD/DCA for however many hours it is.
But, because OP won't know until he gets to the airport, he has to bring his bags and be prepared to fly as scheduled.
and the agent IME is way less likely to do it if you've checked or are checking bags. My other point was that I've had the app offer to SDC the domestic leg before so if carrying on there's a chance the app or website may offer it up.