Adding your Known Traveler Number (KTN) to your airline reservation is the specific action that triggers your TSA PreCheck eligibility for that flight. In 2026, once your KTN is verified against your booking details (name, DOB, and gender must match your enrollment exactly), the "TSA PRE" indicator will be printed on your boarding pass. This allows you to enter the expedited security lane, where you don't have to remove your shoes, light jackets, or belts, and you can keep your laptop and 3-1-1 liquids inside your bag. For 2026 travelers, the KTN is a 9-digit "PASS ID" found on the back of your Global Entry, NEXUS, or SENTRI card. By adding it to your frequent flyer profile once, it will auto-populate for all future bookings, ensuring you save roughly 20–40 minutes at the airport by bypassing the standard "shoes-off" security lines that often bottle-neck major U.S. terminals.