How to Add TSA Precheck to Delta?
There are two ways to add TSA PreCheck to Delta:
When you book your flight: If you have already been approved for TSA PreCheck, you can add your Known Traveler Number (KTN) to your Delta reservation when you book your flight. To do this, log in to your Delta SkyMiles account and enter your KTN in the "Known Traveler Number/Trusted Traveler" field.
After you book your flight: If you have already booked your flight and you have not yet been approved for TSA PreCheck, you can still add your KTN to your reservation. To do this, log in to your Delta SkyMiles account and go to your "My Trips" page. Click on the "Edit Passenger Information" button for the flight you want to add your KTN to. Enter your KTN in the "Known Traveler Number/Trusted Traveler" field and click on "Save Changes."