Originally Posted by darthlemsip

From experience with other TSA Pre approved airlines, if your KTN doesn't stick (as happens on roughly half my AA flights), or you can't get your airline to add it (as is the case with my JFK-MXP flight in April), then it can almost always be resolved at a check-in desk - however they usually ask for the card, which non-US citizens don't have, so make sure you have a copy of your KTN handy.