To add TSA PreCheck to your American Airlines booking, you can follow these steps: First, ensure that you are eligible for TSA PreCheck. You can do this by visiting the TSA PreCheck website and submitting an application. Once you are approved, you will receive a TSA PreCheck Known Traveler Number (KTN). Log in to your American Airlines account and navigate to your trip details. Click on the "Add/Edit Passenger Information" option. Enter your TSA PreCheck KTN in the "Known Traveler Number" field for each passenger in your booking. Save your changes and you should see the TSA PreCheck indicator on your boarding pass for the eligible flights. Alternatively, you can also add your TSA PreCheck information to your booking during the online check-in process or by calling American Airlines customer service.