Originally Posted by
lg20
They will cancel duplicates where you have two tickets on one flight. Or when it is physically impossible to fly (either in the air at the same time or impossible connections SEA-DCA, SAN-OGG with less than an hour between, though I don't think the logic will automatically find those latter ones).
The same flight on successive days should be fine. You could easily be back to SFO the next morning before flying back again. I've had two GEG-SEA flights on the same day.
Agree that there is no problem with flights two days in a row. I've done it to hedge my bets. I have had two impossible reservations when I hadn't decided which city I was going to fly home from and one did not get cancelled, although I did cancel one well before the flight date.
I believe you can cancel the first reservation in such a way that you would only be charged the change fee if you used the value of the ticket again. I think I remember that as one of the choices when I recently paid a change fee for my daughter's ticket.