KTN, or Known Traveler Number, is a unique number issued by trusted traveller programs such as TSA Pre✓. If you provide this number when booking your ticket, you can use the TSA Pre✓ lane at the airport security checkpoints. If you’ve already booked your ticket or did not enter your KTN at the time of booking, you can easily add it later by phone (), online via My Trips, or during online check-in.