You cannot add TSA PreCheck to your current flight after checking in, but you can enroll for future trips

Once you have checked in for a flight, your boarding pass is locked in without PreCheck status. TSA PreCheck must be added before you check in — either when you book your ticket or during online check-in up to 24 hours before departure. If you have already checked in without it, you will go through standard security screening for that flight.

The good news is that TSA PreCheck enrollment is separate from any single flight. When you enroll in the program, you receive a Known Traveler Number (KTN) that stays with you for five years. You can use this number on all future bookings with participating airlines, which means every flight after enrollment will have PreCheck access — as long as you add your KTN before checking in.

Key Takeaways

  • Your boarding pass is finalized at check-in, so PreCheck cannot be added after that point for the current flight.
  • You must enter your Known Traveler Number when booking or during online check-in to access PreCheck screening on any flight.
  • TSA PreCheck enrollment is a separate five-year membership that applies to all future trips once you have your KTN.
  • If you checked in without PreCheck by mistake, contact your airline to see if they can reissue your boarding pass before you reach security.

How to add your KTN before checking in

When you book your ticket online, most airlines have a field for your Known Traveler Number. Enter your nine-digit KTN there, and it will appear on your boarding pass. If you did not add it at booking, you can still add it during online check-in, which opens 24 hours before departure for most carriers.

Log into your airline's website or app, find your reservation, and look for a section labeled "Manage Booking," "Trip Details," or "Add Known Traveler Number." Enter your KTN and save the changes. Your new boarding pass will show TSA PreCheck may be able to access. This works for most major U.S. airlines including American, Delta, United, Southwest, and Alaska.

If you are checking in at the airport counter or kiosk, you can ask the agent to add your KTN before they print your boarding pass. This is your final note to add it before security screening.

What happens if you reach security without PreCheck on your boarding pass

If your boarding pass does not show PreCheck, you will be directed to standard security lanes. You will need to remove your shoes, belt, and light jacket; take out your laptop and liquids; and place everything in a bin. The process takes longer and is more involved than PreCheck screening.

Some airports have separate PreCheck and standard lanes, while others use a mixed approach. Either way, TSA officers check your boarding pass to determine which screening process you go through. Telling them you have PreCheck enrollment will not change this — only the boarding pass notation matters at the checkpoint.

How to enroll in TSA PreCheck if you have not yet

TSA PreCheck enrollment happens through the official TSA website at tsa.gov or through a trusted traveler program enrollment center. You will need to provide personal information, pay the enrollment fee (currently $78 to $85 depending on your state), and schedule an in-person appointment at an enrollment center.

The appointment takes about 10 to 15 minutes. You will bring a valid passport or state ID, proof of citizenship or lawful permanent residency, and proof of your current address. After your background check clears, you will receive your Known Traveler Number by email, usually within two to three weeks.

Once you have your KTN, you can use it on all future bookings. You do not need to enroll again for each flight — the five-year membership covers unlimited trips.

If you already checked in without PreCheck

If you have already checked in and realized you forgot to add your KTN, contact your airline when ready. Some airlines can reissue your boarding pass at the counter or through their app if you have not yet passed through security. This is not always possible, especially if you are close to your departure time, but it is worth asking.

If the airline cannot reissue your boarding pass, you will go through standard security screening for that flight. This does not affect your PreCheck status for future flights — you can still use your KTN on your next booking.

Which airlines accept TSA PreCheck at check-in

All major U.S. airlines that fly domestic routes accept TSA PreCheck. This includes American Airlines, Delta Air Lines, United Airlines, Southwest Airlines, Alaska Airlines, JetBlue, Spirit Airlines, Frontier Airlines, and Allegiant Air. If you fly internationally, PreCheck applies only to your U.S. departure and return flights, not to flights within other countries.

Some regional carriers and smaller airlines may not participate in the program. If you are unsure whether your airline accepts PreCheck, check their website or call their customer service before you book.

Frequently Asked Questions

Can I add my KTN to my boarding pass after I check in online?

Yes, as long as you have not yet arrived at the airport. You can log back into your airline's website or app and update your reservation with your KTN up until you reach the security checkpoint. Once you have scanned your boarding pass at security, it cannot be changed.

What if my airline's website does not have a field for my Known Traveler Number?

Some smaller airlines or older booking systems may not have an automated field. Call the airline's customer service line and ask them to manually add your KTN to your reservation. Provide them with your confirmation number and your nine-digit KTN, and they can update it in their system.

Do I need to add my KTN every time I book a flight?

Yes, you need to add your KTN to each individual booking. Your PreCheck membership does not automatically attach to every ticket you purchase — you have to enter it during booking or check-in. Once you add it to a reservation, it stays on that boarding pass.

Will PreCheck work if I am traveling with someone who does not have it?

Yes. You will go through the PreCheck lane, and your companion will go through standard screening. You do not have to travel together through security. PreCheck is tied to your boarding pass, not to your travel group.

Can I get a refund if I enrolled in PreCheck but forgot to use my KTN?

TSA does not refund PreCheck enrollment fees based on usage. Your membership is valid for five years from the date of enrollment, regardless of how many times you use it. If you have not used your KTN yet, you can start using it on your next booking.