I noticed my SEA-IAH-PHL flights for Sunday AM were no longer listed in Worldspan or Apollo, so I called. It took some time for them to find my flight, as they claimed that my 12:30am flight was listed with the flights from the day before. My guess was correct, and the flights are now officially cancelled. In rebooking I reminded them that I have another itinerary out of PHL 4 1/2 hours after my return from this trip. At first, they refused to change the other itinerary despite the fact that their airline's cancelled flights are what are preventing me from getting to PHL in time. I waited a LONG time while a (presumably swamped) supervisor decided whether my reasonable request to simply delay the other itinerary 24hrs so I could return from SEA was worthy enough. They decided that it was.