A couple of years back 2 of us went from Seattle to Washington DC for Memorial Day weekend. We left early Saturday morning and tried to return Monday. We were taxiing out from DCA to JFK and would've been able to get out on the morning flight in JFK but because of weather we ended up sitting on the taxiway for 2 hours before we returned to the gate and cancelled the flight. Everything else was really full that day. I ended up having to burn 50000 miles on United to get 2 first class tickets back! I suppose it is possible but have many backups and be prepared to buy an expensive last minute ticket if you must.