Make sure you currently have a valid TSA PreCheck membership with a Known Traveler Number (KTN) before adding TSA PreCheck to your Japan Airlines reservation. How To Add TSA Precheck To Japan Airlines In the designated field on the Japan Airlines website, enter your KTN throughout the booking process. If you’ve already made a reservation, you can change it online or by calling Japan Airlines customer support. To prevent problems, make sure your name and KTN match your TSA PreCheck profile. The benefits of TSA PreCheck are applicable to aircraft arriving and departing from the United States, not just flights within Japan.