Access your Mileage Plus account on the United Airlines website to start applying TSA PreCheck to your reservation. Your Known Traveler Number (KTN) can be found under Personal Information after selecting the Profile area. If it isn't there already, add your KTN and save the modifications. How Do You Add TSA PreCheck to United Airlines can be integrated Select your booking under "Manage Reservations" and use your KTN to edit the Traveler Information section for active reservations. There are other options as well, such giving your KTN to a United representative at the airport or including it while purchasing online. Your boarding pass will display TSA PreCheck benefits if you meet all the requirements. Verify that your KTN corresponds to your travel and is accurate.