Doesn't the airline have the obligation to get you to your FINAL destination? So for example shouldn't US/AA have to pay for the OP's expenses of getting from DCA to BWI? IMHO, airports like DCA/BWI/IAD, JFK/EWR/LGA, LAX/SNA/LGB, SFO/OAK, FLL/MIA etc are not that close together and I would hope in the event an airline rebooks you from one of these airports to another they will reimburse you the cost of transportation.