An airport inspection in the United States is handled by one of two federal agencies depending on where you’re flying. The Transportation Security Administration (TSA) screens you and your bags before every departing flight. U.S. Customs and Border Protection (CBP) inspects you when you arrive from another country. The two processes have different rules, different penalties, and different rights, and several of the TSA rules changed in 2025.
ID You Need to Board
Every passenger 18 and older must show valid identification at the TSA checkpoint.1Transportation Security Administration. Acceptable Identification at the TSA Checkpoint Since May 7, 2025, a domestic driver’s license or state ID has to be REAL ID-compliant, marked with a star in the upper corner. A standard license without that marking is no longer accepted for boarding.2Transportation Security Administration. REAL ID
If your license doesn’t have the star, a valid U.S. passport works instead. Showing up with neither can mean missing your flight.
What Happens at the TSA Checkpoint
After the ID check, your carry-on bags go on the belt for X-ray, and you walk through either a metal detector or an Advanced Imaging Technology (AIT) body scanner. The AIT uses radio waves to detect metallic and non-metallic objects under clothing. You can ask to use the metal detector instead, but that choice comes with a pat-down.
What You Have to Take Off
The Department of Homeland Security ended the shoes-off requirement at domestic checkpoints in mid-2025, so you can keep your shoes on during standard screening.3Transportation Security Administration. DHS to End Shoes-Off Travel Policy Outerwear and belts still come off in standard lanes. Laptops and other large electronics generally have to come out of your bag and go in a separate bin.
The laptop-out rule is fading at airports with newer computed tomography (CT) scanners, which produce a rotatable 3D image and let officers see inside a bag without unpacking it. Deployment isn’t complete, so watch the signs and listen to what officers tell you at each checkpoint.
The PreCheck Lane
TSA PreCheck members use a dedicated lane and keep shoes, belts, and light jackets on. Laptops and liquids stay in the bag.4U.S. Customs and Border Protection. TSA PreCheck Enrollment runs $77 to $85 depending on the provider and is good for five years.5Transportation Security Administration. TSA PreCheck
What You Can and Can’t Pack
The 3-1-1 Liquids Rule
Liquids, aerosols, gels, creams, and pastes in carry-ons must follow the 3-1-1 rule. Each container is limited to 3.4 ounces (100 milliliters), everything has to fit in one quart-sized clear plastic bag, and you’re allowed one bag per person.6Transportation Security Administration. Liquids, Aerosols, and Gels Rule Checked bags have no liquid limit; they’re screened separately with explosive detection systems.7Transportation Security Administration. Electronic Baggage Screening Program
Prohibited Items
If a prohibited item shows up during screening, the bag gets pulled for a hand search. You can surrender the item, walk back to the ticket counter to move it into checked luggage, or, depending on what it is, face a referral to law enforcement. Knives and other sharp objects are banned from the cabin. Sporting equipment like bats has to be checked.8Transportation Security Administration. What Can I Bring?
Serious items carry serious penalties. A loaded firearm found at a checkpoint brings a civil penalty of $3,000 to $12,210 plus a criminal referral. Repeat violations run $12,210 to $17,062. Explosives start at $10,230 and also trigger criminal referral.9Transportation Security Administration. Civil Enforcement TSA catches firearms at checkpoints almost every day nationwide.
Flying With a Firearm
You can travel with a firearm, but only in checked baggage, and only if you follow every step. The firearm has to be unloaded and locked in a hard-sided container that can’t be easily pried open. You must declare it at the airline ticket counter each time you check it. TSA treats a firearm as “loaded” if a live round is in the chamber, cylinder, or an inserted magazine; for civil penalty purposes, TSA also considers a firearm loaded when the gun and ammunition are both accessible to the passenger.10Transportation Security Administration. Transporting Firearms and Ammunition State and local possession laws still apply at your destination, and confirming them is on you.
Medical Items, Service Animals, and Head Coverings
Medications, baby formula, and breast milk are exempt from the 3-1-1 rule. TSA allows medically necessary liquids in reasonable quantities, but you have to declare them at the checkpoint so they can be inspected separately. If one of them alarms during testing, it may not be allowed through. Breast milk is permitted in any quantity, fresh, frozen, or partially thawed, even if the child isn’t with you, and the ice packs and coolers used to store it are also exempt.11Transportation Security Administration. Medical
CPAP machines, BiPAP machines, and nebulizers come out of their cases and go through the X-ray separately. Facemasks and tubing can stay in the case, and you can put the device in a clear plastic bag before it hits the belt.12Transportation Security Administration. Am I Allowed to Carry My CPAP Machine Onboard the Plane
Tell the officer if you’re traveling with a service animal. TSA will not separate you from the animal. You can walk through the metal detector together or send the animal through on a leash. If the detector alarms, both of you go through additional screening, including a pat-down; the officer will ask for your help before touching the animal. Collars, harnesses, vests, and leashes go through X-ray, though items you need to keep control of the animal don’t have to be removed.13Transportation Security Administration. I Have a Service Animal, What Type of Screening Should I Expect? If you leave the secured area to relieve the animal, you’ll be screened again, and you can ask to move to the front of the line when you return.
Religious head coverings can stay on during screening but may trigger a pat-down, which is conducted by an officer of the same sex. If the alarm can’t be resolved that way, you can ask to remove the covering in a private screening area.14Transportation Security Administration. May I Keep Head Coverings and Other Religious, Cultural or Ceremonial Items on During Screening?
Additional Screening and Your Rights
You can be pulled aside for extra screening for any of several reasons: randomly, because something in your documents raised a flag, or because an alarm went off. Passengers who see “SSSS” (Secondary Security Screening Selection) printed on the boarding pass are routed automatically to enhanced screening: a thorough pat-down, swab tests for explosive residue on your hands and belongings, and a hand search of your carry-on. Add 15 to 45 minutes if those letters appear.
Pat-Downs
At any point during screening you can request a private pat-down and have a witness of your choice present. The pat-down is conducted by an officer of the same sex.15Transportation Security Administration. What Can I Expect During Pat-Down Screening? Officers are trained to accommodate these requests, so ask.
If You Keep Getting Flagged
Repeated secondary screening you believe is a mistake can be addressed through the DHS Traveler Redress Inquiry Program (DHS TRIP). You submit an application at trip.dhs.gov describing your experience, along with a copy of your unexpired passport or government-issued photo ID. After the case is reviewed and closed, you receive a Redress Control Number to add to future reservations, which can reduce the chance of repeated flagging.16DHS Traveler Redress Inquiry Program. Frequently Asked Questions
Arriving From Abroad: CBP Inspection
Coming into the United States from another country, you go through CBP. Officers verify your identity, check your immigration status, and review a customs declaration listing what you’re bringing in.17U.S. Customs and Border Protection. The CBP Inspection Process U.S. citizens are admitted once citizenship is verified; non-citizens face further questioning, and their documents are examined against immigration law.18U.S. Customs and Border Protection. Immigration Inspection Program
Food, Plants, and Agricultural Items
Meats, fruits, vegetables, soil, and live plants are all subject to inspection, and some are banned outright. Failing to declare a prohibited agricultural item can bring a civil penalty of up to $1,000 for a first offense involving personal quantities.19U.S. Customs and Border Protection. Bringing Agricultural Products Into the United States Commercial quantities trigger far higher penalties; the underlying statute allows fines up to $250,000 per violation for entities and up to $50,000 for individuals.20Office of the Law Revision Counsel. 7 USC 7734 – Penalties for Violation Even a piece of fruit from the plane can trigger a fine if you don’t declare it.
The $800 Duty-Free Exemption
Returning U.S. residents can bring back up to $800 in goods purchased abroad without paying duty, as long as the items travel with them. Travelers arriving directly from American Samoa, Guam, the Northern Mariana Islands, or the U.S. Virgin Islands get a $1,600 exemption, though no more than $800 of that total can come from goods acquired outside those territories.21eCFR. 19 CFR Part 148 Subpart D – Exemptions for Returning Residents Anything over the limit is subject to duty, and the full value has to be declared.
The $10,000 Currency Rule
Federal law requires anyone transporting more than $10,000 in currency or monetary instruments into or out of the United States to file FinCEN Form 105.22Office of the Law Revision Counsel. 31 USC 5316 – Reports on Exporting and Importing Monetary Instruments The threshold captures the combined total of cash, traveler’s checks, money orders, and certain other negotiable instruments, in both U.S. and foreign currency.23Financial Crimes Enforcement Network. FinCEN Form 105
There’s no cap on how much you can carry. The rule is only that you report it. Failing to report accurately, or splitting amounts to stay under the threshold, brings severe consequences. CBP can seize the whole amount, not just the portion over $10,000. Criminal penalties reach fines up to $500,000 and up to 10 years in prison.24USAGov. How Much Money Can You Bring Into and Out of the U.S. Dividing cash between traveling companions doesn’t get around the rule; the filing obligation applies to the total amount carried by or on behalf of a person.
Searches of Phones and Laptops
CBP officers can search electronic devices at the border under the border search exception to the Fourth Amendment. Courts have long treated routine, warrantless searches at the border as constitutionally reasonable.25Constitution Annotated. Amdt4.6.6.3 Searches Beyond the Border
CBP policy splits device searches into two levels. A basic search is a manual review by the officer of content already on the device, such as photos, messages, or files, without connecting any external equipment. No suspicion is required. An advanced search means connecting the device to external equipment to copy or analyze contents; it requires reasonable suspicion of a legal violation or a national security concern and must be approved by a senior CBP manager before it begins.26U.S. Customs and Border Protection. Border Search of Electronic Devices at Ports of Entry Refusing to provide access won’t stop the inspection; CBP can detain the device for further examination, which may delay your entry processing significantly.
Trusted Traveler Programs
Two federal programs shorten your time in these lines. TSA PreCheck covers domestic security screening and costs $77 to $85 for five years.5Transportation Security Administration. TSA PreCheck Global Entry covers international arrivals, letting you skip the standard CBP inspection line for a kiosk or automated process. It costs $120 for five years and includes PreCheck benefits.27U.S. Customs and Border Protection. How to Apply for Global Entry
Both require a background check and an in-person interview with a CBP officer. The application fee is non-refundable if you’re denied. Customs violations, criminal history, or incomplete applications can lead to denial or revocation.
For frequent international travelers, Global Entry is usually the better value since it covers both customs and security. If you only fly domestically, standalone PreCheck is cheaper. Many travel credit cards reimburse one or both fees, so check your card benefits before paying out of pocket.