Domestic US Carry-On Rules: What Every Airline Allows in 2026

Flying between US cities is one of the most carry-on-friendly situations in air travel. There are no weight limits to worry about, the major carriers include a full-size carry-on in the base fare, and TSA rules are well-established and consistent across airports. Here is what you need to know for each carrier and for navigating security.

The Standard: One Carry-On Plus One Personal Item

On all major full-service US carriers — American Airlines, Delta Air Lines, United Airlines, Alaska Airlines, Southwest Airlines, JetBlue, and Hawaiian Airlines — a standard economy fare includes:

• One carry-on bag: fits in the overhead bin, typically 22×14×9 inches maximum
• One personal item: fits under the seat in front, typically 18×14×8 inches or smaller

Both items are free on standard (non-basic-economy) tickets. There are no weight limits on either item. You can carry a heavy laptop bag and a fully packed carry-on suitcase without any charge, as long as both fit within size limits.

Ultra-Low-Cost Carriers: Carry-On Fees Apply

Spirit Airlines, Frontier Airlines, and Allegiant Air operate on a different model. Their base fares include only a small personal item that fits under the seat. Adding a carry-on bag for the overhead bin costs extra.

Spirit Airlines: carry-on bags cost approximately $40–$100 depending on the route and when you add the bag. Booked at check-in is cheaper than at the gate. Spirit's carry-on size limit is 22×18×10 inches — slightly larger in two dimensions than most carriers.

Frontier Airlines: carry-on fees range from approximately $35–$99 depending on fare type and booking timing. Frontier Elite 20K and higher members get one free carry-on. Size limit is 24×16×10 inches.

Allegiant Air: carry-on fees are similar to Spirit and Frontier. The base "Basic" fare permits only a small personal item. Allegiant's size limit is 22×16×9 inches.

If you are flying one of these carriers with only a bag that fits under the seat, you avoid the fee entirely. Many experienced travelers flying Spirit or Frontier bring only a small backpack that meets the personal item dimensions.

Basic Economy on the Big Three

American Airlines, Delta, and United each have a basic economy fare tier that restricts carry-on rights:

• American Airlines Basic Economy: limited to one personal item under the seat. No overhead bin carry-on unless you have AAdvantage elite status or a co-branded credit card.
• Delta Basic Economy (Main Cabin Basic): one personal item only. Carry-on in the overhead bin costs extra or requires Medallion status.
• United Basic Economy: one personal item only, same restrictions.

If you book a basic economy fare on any of these airlines, check whether you have status or a qualifying credit card before assuming your overhead bag goes free.

Southwest now sells a Basic fare, which still includes one carry-on and one personal item. Checked-bag fees apply to Basic, Choice, and Choice Preferred without eligible benefits; Choice Extra and A-List Preferred include two standard bags free on eligible Southwest flights. See fare rules.

Size Limits by Carrier

Note: all size limits include wheels and handles. The stated dimensions refer to the total external size of the bag.

TSA Rules That Apply to All US Domestic Flights

TSA applies the same screening rules regardless of which US airline or route you are flying:

Liquids (3-1-1 rule): liquids, gels, and aerosols must be in containers of 3.4 oz (100 ml) or smaller. All containers must fit in one quart-sized clear plastic bag (approximately 1 litre). One bag per passenger.

Electronics: laptops must be removed from bags and placed in a separate bin. Tablets and cameras vary by checkpoint — some require removal, others do not. When in doubt, remove.

Shoes: most US checkpoints require shoes to be removed and placed in a tray. TSA PreCheck members do not need to remove shoes.

TSA PreCheck: if you have Global Entry or TSA PreCheck enrollment, you use dedicated lanes that are significantly faster and require fewer items to be removed.

Prohibited items: the TSA prohibited items list applies to all domestic flights. Key carry-on restrictions include lithium batteries over 100Wh (airline permission required for 100–160Wh), sharp objects over 7 cm blade length, and most firearms (which may only travel in checked bags in a locked hard case).

How Strictly Are Bag Size Limits Enforced?

US domestic enforcement is inconsistent by design — it is left largely to individual gate agents and their discretion.

Tighter enforcement:

• Full flights where bin space is at a premium
• Airlines that actively charge for carry-on (Spirit, Frontier) have financial incentive to check
• Gates where sizers are present and visibly positioned at the boarding line

More lenient enforcement:

• Off-peak flights with plenty of overhead space
• Regional airports on small routes
• When boarding is already running behind

A bag that is slightly over the sizer limit (2–3 cm in one dimension) is frequently accepted without comment. A bag that is obviously oversized — a large duffle or a 28-inch hard-side suitcase — will be gate-checked on almost any US domestic flight.

Tips for City-Hopping the US Carry-On Only

If you are making multiple stops across US cities on a single trip, these practices keep things smooth:

Pack for the strictest carrier on your itinerary. If one leg is on Spirit and another is on Delta, size your bag to Spirit's limit (which is actually slightly more generous in some dimensions than Delta's).

Use the overhead bin strategically. On short domestic hops (under 2 hours), overhead space fills from the back to the front as passengers board by zone. Boarding early (status, a credit card benefit, or a paid upgrade) gives you better bin access.

Gate-check voluntarily on full regional flights. On regional jets (CRJ-200, ERJ-145), overhead bins are very small and even standard-compliant bags often need to be gate-checked. Proactively asking to gate-check at the jetway is faster than being turned away at the door. Gate-checked bags on domestic flights are returned to you at the jetway upon arrival, not at baggage claim.

Keep liquids and valuables accessible. If your carry-on gets gate-checked, you want your toiletries, laptop, and documents to be in your personal item, not buried in the bag now headed to the hold.