To verify if your Known Traveler Number (KTN) has been successfully applied to your flight, you should look for the TSA PreCheck logo or the text "TSA PRE" prominently displayed on your boarding pass. This indicator is usually located near your name, the barcode, or in the top corner of the document (both digital and printed versions). If you see your KTN (the actual 9-digit number) printed on the pass, that is generally for your reference, but the presence of the PreCheck logo is the only thing that allows you to enter the expedited lane. If the logo is missing, it means the airline system did not link your KTN to that specific reservation, or you were not selected for expedited screening for that flight. It is important to check this before you head to the airport; if it is missing, you can often go to the airline's "Manage Trip" section on their app or website to manually re-enter your KTN, or ask a gate agent at the check-in counter to reprint your pass with the status included.