To add TSA PreCheck to your Delta Air Lines reservations, follow these steps:

Apply for TSA PreCheck: If you haven't already, you need to apply for TSA PreCheck through the TSA PreCheck website or at an enrollment center. Once approved, you'll receive a Known Traveler Number (KTN).

Make a Reservation: Book your flight with Delta Air Lines through their website, mobile app, or by calling their reservations hotline.

Access Your Reservation: After booking your flight, access your reservation through the Delta website or app. Log in to your Delta account if prompted.

Add Your KTN: Look for an option to add your Known Traveler Number (KTN) to your reservation. This is typically found under the passenger information or personal details section of your reservation.

Enter Your KTN: Enter your Known Traveler Number (KTN) into the designated field. Double-check to ensure you input it correctly.

Save Changes: After entering your KTN, save the changes to your reservation.

Check for TSA PreCheck: Review your reservation to ensure that TSA PreCheck has been successfully added. You should see a notification indicating that you are eligible for TSA PreCheck on your boarding pass.

Print or Retrieve Boarding Pass: Once you've completed these steps, either print your boarding pass or retrieve it electronically through the Delta website or mobile app. Your TSA PreCheck status should be indicated on the boarding pass.

By following these steps, you can add TSA PreCheck to your Delta Air Lines reservations and enjoy expedited security screening at participating airports.