How Do You Add TSA PreCheck® to Southwest Airlines? Before adding TSA PreCheck® to your Southwest Airlines reservation, make sure you have a KTN obtained from your TSA PreCheck® registration. Navigate to the “Travel Info” area under your profile after logging into your Southwest Airlines account. Put your KTN in the space provided. To update an existing reservation using your KTN, go to the “My Trips” section of the Southwest website, choose the booking, and enter your information. You will benefit from quicker security screening on your flights thanks to this approach.