Originally Posted by cepheid

Your "discount travel certificate" is paper, right? If so, then officially, no, you cannot combine them. Itineraries where an e-cert is applied cannot be held, and to use a paper voucher with an online booking, you have to be able to hold the itinerary. Some folks have claimed success by holding the original itinerary, calling Web Support (not Reservations) and having them manually apply the e-cert but leaving the itinerary on hold, then completing the booking at the airport with the paper voucher... I have not tried this so I can't speak from personal experience as to the success of this method.