You can add TSA PreCheck to your Southwest reservation after check-in, but only during a narrow window

Once you have checked in to your Southwest flight, you can still add TSA PreCheck to your booking—but you have a limited amount of time. Southwest allows you to add it up to 24 hours before your scheduled departure, which means if you checked in online 24 hours early, you may have already missed the window. The process happens through your Southwest account, not at the airport, and requires your Known Traveler Number (KTN)—the nine-character code TSA issues when you enroll in PreCheck separately.

The key difference between adding PreCheck before and after check-in is that after check-in, you are working against the clock. Southwest's system will not let you add it once you are within 24 hours of departure, so if your flight leaves tomorrow morning, you cannot add it today. If you are still within that 24-hour window, the steps are straightforward and take about five minutes.

Key Takeaways

  • You can add your TSA PreCheck KTN to a Southwest reservation up to 24 hours before departure, even after you have checked in online.
  • You need your Known Traveler Number from TSA before you can link it to your Southwest booking—PreCheck enrollment and flight booking are separate processes.
  • Adding PreCheck after check-in happens in your Southwest account under "Manage Reservations," not at the airport counter.
  • Once you add your KTN to a reservation, it appears on your boarding pass automatically, but only if you do it before the 24-hour cutoff.
  • If you miss the window, you can still go through PreCheck screening at the airport if you have an active KTN, but your boarding pass will not display the PreCheck indicator.

Where to find the option in your Southwest account

Log into your Southwest account on the website or mobile app and go to "Manage Reservations." Enter your confirmation number and the phone number or email associated with your booking. Once you pull up your reservation, look for a section labeled "Passenger Details" or "Trip Details"—the exact wording varies slightly between the website and app, but it is always near the top of your reservation summary.

In that section, you will see a field for "Known Traveler Number" or "KTN." This is where you enter the nine-character code from your TSA PreCheck enrollment confirmation. If you do not see this field, your reservation may be too close to departure (within 24 hours) or you may be looking at a different part of your account. Double-check that you are in the reservation itself, not just your account dashboard.

Entering your Known Traveler Number correctly

Your KTN is a nine-character alphanumeric code that TSA sends you when you complete PreCheck enrollment and pay the fee. It appears on your TSA PreCheck approval notice, which you receive by email or mail depending on how you enrolled. The code looks something like "ABC123DEF" and is case-sensitive in some systems, though Southwest's system typically accepts it in any case.

Type it exactly as it appears on your approval notice, with no spaces or dashes. If you cannot find your KTN, log into your TSA account at tsa.gov or call the TSA PreCheck enrollment center where you enrolled. Do not guess or use a partial number—Southwest will reject an incorrect KTN and you will have to try again. Once you enter it and save, the system confirms the entry within seconds.

When the change shows up on your boarding pass

After you add your KTN to your reservation, it takes a few minutes for Southwest's system to update. When you check your boarding pass—whether you pull it up in the app, print it, or retrieve it at the airport—you should see "TSA PreCheck" printed near your name or confirmation number. This indicator tells TSA agents at security that you have an active PreCheck membership and are may be able to access for expedited screening.

If you added your KTN but do not see it on your boarding pass, refresh the page or close and reopen the app. If it still does not appear and you are still within the 24-hour window, contact Southwest customer service to confirm the entry went through. Sometimes a typo in the KTN or a system delay causes the indicator to not display, and Southwest can verify whether your number is correctly linked.

What happens if you miss the 24-hour important date

If you are past the 24-hour mark before departure, Southwest's system will not allow you to add your KTN through "Manage Reservations." The field either disappears or becomes locked. You cannot add it at the airport counter or gate—the cutoff is firm and applies whether you are checking in online, at a kiosk, or with an agent.

However, you can still use TSA PreCheck screening at the airport. Bring your physical TSA PreCheck card or your approval notice with you, and tell the TSA agent at security that you have an active KTN. They can manually verify your PreCheck status in their system and direct you to the PreCheck lane, even though your boarding pass does not display the indicator. This is slower than having it on your boarding pass, but you still get PreCheck screening.

Troubleshooting common problems

If you enter your KTN and Southwest rejects it, the most common cause is a typo. Double-check each character against your approval notice, paying attention to the difference between the number zero and the letter O, and the number one and the letter I. Some people also accidentally include spaces or dashes that are not part of the actual code.

If you are certain the number is correct but Southwest still rejects it, your PreCheck enrollment may have expired or not been fully processed. TSA PreCheck is valid for five years from the date you enroll, so if you enrolled more than five years ago, you need to renew before the KTN will work. You can check your enrollment status at tsa.gov by logging into your account. If your enrollment is current and Southwest still rejects the number, contact Southwest customer service with your confirmation number and KTN—they can escalate it to their technical team.

Adding PreCheck to multiple passengers on the same reservation

If you booked a flight for multiple passengers, you need to add each person's KTN separately. When you pull up your reservation in "Manage Reservations," you will see a list of all passengers. Click on each passenger's name or details to access their individual KTN field. Enter the correct KTN for each person—do not use the same number for everyone unless you are traveling with family members who share an enrollment (which is not typical).

Each passenger's boarding pass will then display their own PreCheck indicator once the system updates. If one passenger does not have a KTN yet, you can add it for the others and come back to add theirs later, as long as you are still within the 24-hour window. If you are adding PreCheck for a child or dependent, make sure you have their actual KTN from their own TSA PreCheck enrollment—children can enroll separately and receive their own code.

Frequently Asked Questions

Can I add TSA PreCheck at the Southwest ticket counter or gate?

No. Southwest only allows you to add your KTN through your online account in "Manage Reservations." The ticket counter and gate agents cannot add it for you, even if you are within the 24-hour window. You must do it yourself through the website or app before you arrive at the airport.

What if I have TSA PreCheck but do not know my KTN?

Log into your account at tsa.gov and look for your enrollment status or approval notice. Your KTN is printed on the approval notice you received when you enrolled. If you cannot find it online, call the TSA PreCheck enrollment center where you completed your enrollment—they can provide your number over the phone.

Does adding my KTN after check-in cost extra?

No. Adding your KTN to your reservation is free. You pay for TSA PreCheck enrollment separately when you enroll with TSA, not when you link it to individual flights. Southwest does not charge a fee to add it to your booking.

Will my PreCheck status carry over to future Southwest flights?

No. You need to add your KTN to each Southwest reservation individually. Once you add it to one flight, it does not automatically appear on your next booking. However, if you link your Southwest account to your TSA PreCheck profile (if that option becomes available), future bookings may populate it automatically—check Southwest's website for the latest account linking options.

What if my flight is cancelled and rebooked?

If Southwest cancels your flight and rebooks you on a different one, you will need to add your KTN to the new reservation as well. The KTN does not transfer automatically to the new booking. Log into "Manage Reservations" with your new confirmation number and add it the same way you did for the original flight, as long as you are still within 24 hours of the new departure time.