To add your TSA PreCheck to your American Airlines reservation, you can do so during the booking process or by adding it to an existing reservation. You will need to log in to your account on the airline's website or mobile app and select the "Manage Reservations" option. From there, select the flight you want to add your TSA PreCheck to and click on "Add/Edit TSA PreCheck Pass ID" to enter your Known Traveler Number (KTN).
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