How Does TSA Checkpoint Screening Work at US Airports?

Summary

The steps

1. 1

   Step 1: Document Check - Present Your ID and Boarding Pass

   The first station at every TSA checkpoint is the document check. A TSA officer or a Credential Authentication Technology (CAT) scanner confirms that your identity document is valid, that it matches your face, and that your boarding pass is for a flight departing that day.

   Under 49 CFR 1540.105 (Responsibility of passengers and other individuals), travelers must present valid identification when directed by a TSA officer. As of May 7, 2025, TSA accepts only the following documents for domestic air travel:

   • A REAL ID-compliant driver's license or state ID (look for the star marking in the upper corner)
   • A US passport or passport card
   • A DHS trusted traveler card: Global Entry, NEXUS or SENTRI
   • A military ID
   • Another TSA-accepted form of identification (full list at TSA.gov)

   Standard driver's licenses without the REAL ID star are no longer accepted for domestic commercial flights. If your license lacks the star, bring a US passport instead.

   Practical note: CAT scanners at many large hub airports can verify your identity without a printed boarding pass, reading your ID directly. Check whether your airport has CAT lanes before you travel.

   Do this

   Check your driver's license for the REAL ID star before travel day.,If your license is not REAL ID-compliant, bring a US passport or passport card.,Pull up your mobile boarding pass and raise screen brightness before joining the security line.

   Example

   A traveler whose state license does not carry the REAL ID star can use a US passport at the document check without any issue.

   Best practice

   Keep your ID and boarding pass in a dedicated outer pocket so you can present them in seconds without digging through your bag at the officer's station.
2. 2

   Step 2: Carry-On X-Ray and Bin Loading

   After the document check, you move to the X-ray conveyor. In a standard lane, TSA requires you to separate items into bins:

   • Laptops and large electronics removed from bags and placed flat in a bin
   • Your quart-sized liquids bag, removed from your carry-on (required under the TSA 3-1-1 rule for carry-on liquids)
   • Shoes, removed and placed in a bin
   • Belts and light jackets, removed
   • Your carry-on bag itself, placed directly on the belt or in a bin

   In a TSA PreCheck lane, none of the above need to be removed. Your carry-on goes through the X-ray as packed, which is the main practical benefit of enrollment for frequent travelers.

   Many large hub airports use Automated Screening Lanes (ASLs). These lanes have individual bins that divert automatically if a second look is needed, so a flagged item does not stop the whole belt. The rules are the same; the lane design reduces bottlenecks.

   Practical note: The most common reason a bag is pulled for a secondary X-ray is a tangled mass of cables, chargers and electronics that the X-ray operator cannot read clearly. Keeping cables in a small pouch and electronics in a single accessible pocket reduces this significantly.

   Do this

   Pack your liquids bag at the very top of your carry-on for quick removal.,Wear slip-on shoes on travel days to speed up bin loading.,Remove your laptop from its sleeve before you reach the belt, not at it.

   Example

   A traveler who packs their liquids bag on top and wears slip-on shoes can load bins in a standard lane without holding up the line.

   Best practice

   Use one bin per category: shoes in one, liquids in one, laptop flat in one. Do not stack items in a single bin; it increases the chance of a secondary X-ray.
3. 3

   Step 3: AIT Body Scanner

   After loading your bins, you step into the Advanced Imaging Technology (AIT) body scanner. TSA uses millimeter-wave scanners at US commercial airports. You stand on the footprint markers, raise your arms in a V shape, and hold still for a few seconds. Millimeter-wave scanners do not use ionizing radiation.

   If the scanner detects an anomaly, a TSA officer will conduct a targeted pat-down of the flagged area only. This is a routine part of the process and is not an indication of suspicion.

   You may opt out of the AIT scanner at any time and request a pat-down instead. Opting out means a full-body pat-down conducted by a same-gender officer.

   Travelers with medical devices, implants or prosthetics should notify a TSA officer before screening. TSA operates a TSA Cares helpline at 1-855-787-2227 for travelers who need advance guidance on disability or medical-related screening. TSA recommends calling at least 72 hours before your flight.

   Practical note: The single most common cause of a scanner alert is items left in pockets: a phone, coins, a key fob, or a forgotten receipt. Emptying pockets into your carry-on before you reach the scanner eliminates this almost entirely.

   Do this

   Empty your pockets completely into your carry-on before stepping into the scanner.,Notify a TSA officer before scanning if you have a medical implant or device.,Call TSA Cares (1-855-787-2227) at least 72 hours before departure if you need screening assistance.

   Example

   A traveler with a pacemaker who notifies the officer before screening will be directed to an alternative screening method that does not involve the AIT scanner.

   Best practice

   Put your phone, keys and wallet in your carry-on before you reach the checkpoint, not in a bin at the last moment. Items in bins can be forgotten or picked up by the wrong person.
4. 4

   Step 4: TSA PreCheck Lane - What Changes and What Does Not

   TSA PreCheck is the TSA's trusted traveler program for domestic and international flights departing US airports, authorized under 49 USC 44919 (PreCheck Application Program). Enrolled members receive a Known Traveler Number (KTN) that they add to their airline reservation. When the KTN is recognized, the boarding pass prints a TSA PreCheck indicator and the traveler uses the dedicated PreCheck lane.

   What PreCheck members do not have to do in the dedicated lane

   • Remove shoes
   • Remove belts
   • Remove light jackets
   • Remove laptops from bags
   • Remove the quart-sized liquids bag from carry-on

   What PreCheck members still must do

   • Present a valid ID and boarding pass at the document check
   • Follow the 3-1-1 liquids rule (the bag just stays in the carry-on)
   • Comply with any additional screening if selected

   PreCheck lanes are available at more than 200 US airports, covering all FAA large-hub and medium-hub commercial airports. Enrollment requires an online application, an in-person appointment at an enrollment center, a background check and a fee. Check TSA.gov/precheck for current enrollment fees and renewal terms.

   CLEAR is a separate, private identity-verification service that uses biometrics (fingerprint or iris scan) to confirm your identity at the document check, then directs you to a TSA lane - standard or PreCheck, depending on your TSA enrollment. CLEAR and TSA PreCheck are complementary services, not interchangeable ones. Having CLEAR does not give you access to the PreCheck lane.

   Do this

   Add your KTN to every airline loyalty profile so the PreCheck indicator prints automatically.,If your boarding pass does not show the PreCheck indicator, use the standard lane; do not enter the PreCheck lane without it.,Renew your PreCheck membership before it expires to avoid a gap in your KTN.

   Example

   A PreCheck member who forgets to add their KTN to a booking will not see the indicator on that boarding pass and must use the standard lane for that specific flight.

   Best practice

   Store your KTN in your airline app profiles and in a secure notes app so you can add it to any booking, including third-party bookings made through travel agencies or booking sites.
5. 5

   Step 5: Additional Screening - What Triggers It and What to Expect

   Additional screening (sometimes called secondary screening) can be triggered by a scanner alert, a random selection, or a flag on your boarding pass such as an SSSS designation (Secondary Security Screening Selection). It is a standard security measure and does not indicate that you are suspected of wrongdoing.

   What additional screening may involve

   • A pat-down by a same-gender TSA officer
   • Explosive Trace Detection (ETD) swabbing of your hands, carry-on or clothing
   • A manual search of your carry-on bag
   • Additional document or boarding pass checks

   Your rights during additional screening

   • You may request a private screening room at any time before or during the pat-down.
   • You may have a companion or witness present.
   • You may ask the officer to explain each step before it is performed.
   • You may file a complaint with the TSA Contact Center at TSA.gov/contact if you believe a procedure was not followed correctly, under TSA's traveler complaint process at 49 CFR 1503 Subpart B.

   If you have a medical device or condition that makes a pat-down uncomfortable, tell the officer before it begins. TSA officers are trained to accommodate medical needs during secondary screening.

   Practical note: An SSSS designation on your boarding pass is most common on one-way tickets purchased close to departure, on international itineraries, or when your reservation details do not exactly match your government ID. Booking round-trip in advance and ensuring your name matches your ID reduces the likelihood of an SSSS flag.

   Do this

   Stay calm and follow officer instructions; cooperation speeds the process for everyone.,Ask for a private room before the pat-down begins if you prefer privacy.,Note the officer's badge number and the approximate time if you intend to file a complaint.

   Example

   A traveler whose carry-on triggers an ETD alert can ask the officer to explain the process; if the swab result is clear, the bag is returned promptly.

   Best practice

   Never joke about prohibited items or security threats at the checkpoint. TSA officers are required to treat all such statements seriously, which will extend your screening time significantly.
6. 6

   Step 6: Prohibited Item Categories - Carry-On vs. Checked Baggage

   TSA maintains a full, searchable list of permitted and prohibited items at TSA.gov. The categories below cover the most common questions. Always verify the current rule for a specific item on TSA.gov or in the TSA app's Can I Bring? feature before you pack.

   Generally prohibited in carry-on bags at all US commercial airports

   • Firearms and firearm parts - prohibited in carry-on under 49 CFR 1540.111(a); may travel in checked baggage only, unloaded, in a locked hard-sided case, declared at airline check-in under 49 CFR 1544.203(f)
   • Ammunition - checked baggage only, subject to airline quantity limits
   • Large knives with blades over 6 cm - checked baggage only
   • Flammable liquids, gases and aerosols beyond permitted quantities
   • Explosive or incendiary devices of any kind
   • Liquids over 3.4 oz (100 ml) per container - exceptions apply for medically necessary liquids and infant formula, which must be declared

   Items that must travel in carry-on, not checked baggage

   • Lithium-ion spare batteries and power banks - prohibited in checked baggage due to fire risk under 49 CFR 175.10(a)(18) (FAA hazardous materials regulations for passenger aircraft); carry-on only

   What this section does not cover

   This section lists general prohibited categories only. TSA rules are updated periodically, and individual items within a category may have specific conditions. Airline baggage policies on size limits, weight limits and fees are separate from TSA rules and vary by carrier. Always verify the current rule for a specific item at TSA.gov before you travel.

   Do this

   Use the TSA app's 'Can I Bring?' feature for any item you are unsure about before packing.,Pack lithium-ion spare batteries in your carry-on, never your checked bag.,Declare firearms at the airline check-in counter before going to the TSA checkpoint.

   Example

   A traveler who wants to bring a full-size shampoo bottle can pack it in checked baggage without restriction, or transfer it to a 3.4 oz travel bottle for carry-on.

   Best practice

   Do a final sweep of your carry-on for prohibited items before you leave home. A prohibited item found at the checkpoint will be confiscated and cannot be retrieved.

TSA Checkpoint Screening: The Same Federal Process at Every US Commercial Airport

Checkpoint Efficiency: Practical Steps to Move Through Faster

What This Guide Does Not Cover

FAQ

What happens at the TSA document check?

A TSA officer or Credential Authentication Technology (CAT) scanner verifies your identity document and boarding pass. As of May 7, 2025, TSA requires a REAL ID-compliant driver's license or state ID, a US passport, a passport card, a DHS trusted traveler card, a military ID, or another TSA-accepted document. Standard non-REAL ID licenses are no longer accepted for domestic flights. Check TSA.gov for the full accepted-ID list.

What do I have to remove at a standard TSA screening lane?

In a standard TSA lane, adults must remove shoes, belts, light jackets, laptops (placed flat in a bin), and the quart-sized clear liquids bag. All of these go into separate bins on the X-ray belt. TSA PreCheck members are exempt from all of these removal steps and use a dedicated lane where their carry-on goes through as packed.

What is the TSA 3-1-1 liquids rule and when does it apply?

The 3-1-1 rule applies to liquids, gels, aerosols, creams and pastes in carry-on bags. Each container must be 3.4 oz (100 ml) or less. All containers must fit in one quart-sized clear zip-top bag per passenger. Medically necessary liquids and infant formula are exempt from the size limit but must be declared at the checkpoint. TSA PreCheck members still follow the 3-1-1 rule; they just do not have to remove the bag from their carry-on.

What are my rights if TSA selects me for additional screening?

You may request a private screening room at any time during additional screening. You may have a companion or witness present. You may ask the officer to explain each step of the process. If you believe a procedure was not followed correctly, you may file a complaint with the TSA Contact Center at TSA.gov/contact. Additional screening is a routine security measure and does not indicate suspected wrongdoing.

Which items are never allowed in a carry-on bag at US airports?

Firearms, firearm parts, large knives (blades over 6 cm), ammunition, explosive or incendiary devices, and flammable liquids beyond permitted quantities are prohibited in carry-on bags at all US commercial airports under 49 CFR 1540.111(a). Firearms may travel in checked baggage when unloaded, in a locked hard-sided case, and declared at airline check-in under 49 CFR 1544.203(f). Lithium-ion spare batteries must travel in carry-on, not checked baggage. Always verify specific items at TSA.gov before you pack.