If you're wondering why TSA PreCheck isn't showing up on your American Airlines boarding pass, several factors could play a role. First, make sure your Known Traveler Number (KTN) is entered correctly in your American Airlines profile. Sometimes discrepancies in personal information between your airline profile and TSA records can cause problems. Additionally, if you recently applied for or renewed your TSA PreCheck membership, it may take some time for it to be reflected in the system. Lastly, certain flights or airports may not support TSA PreCheck, so check to see if your itinerary qualifies. If problems persist, it is advisable to contact American Airlines or TSA directly for assistance.