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Two separate rule sets govern your cabin bag: the airline decides how big it can be, and the TSA decides what can go inside it. The standard US carry-on is 22 x 14 x 9 inches, but Southwest allows 24 x 16 x 10 and the ultra-low-cost carriers enforce a much smaller personal item with a physical sizer at the gate.
Key Travel Facts & Insights
The de facto US standard is 22 x 14 x 9 inches including wheels and handles — the dimension almost every hardshell "carry-on" suitcase is built to. Most US carriers use it.
The exceptions matter. Southwest allows a notably larger 24 x 16 x 10. Spirit and Frontier permit a larger cabin bag but charge for it separately. European carriers frequently impose a cabin bag weight limit — typically 8–10 kg — which US carriers generally do not, and enforce it more actively.
Liquids, gels, aerosols, creams and pastes in your carry-on must be in containers of 3.4 ounces (100 ml) or less, all of which must fit in a single quart-sized clear resealable bag, one such bag per passenger.
The container size is what counts, not how much is in it. A half-empty 8 oz bottle is not permitted; a full 3.4 oz bottle is.
Lithium batteries and power banks must travel in the cabin, never in checked baggage, because of fire risk. This includes spare camera batteries, laptop batteries and portable chargers.
A growing number of airlines now also require power banks to remain visible and not be used or charged during flight. Keep them in the seat pocket rather than the overhead bin.
On carriers where the base fare excludes a carry-on — United Basic Economy, Spirit Go, Frontier Basic, Volaris Zero, Avianca XS, WestJet UltraBasic — arriving at the gate with a full-size bag triggers a charge that is typically several times what the same bag would have cost at booking.
Gate agents at these carriers use a physical sizer and enforce it consistently. The cheapest moment to buy a bag is always the moment you book; the most expensive is the gate.
On small regional aircraft — particularly Bombardier CRJ series flown by SkyWest and others — overhead bins genuinely cannot take a full-size carry-on. Bags are gate-checked at the jet bridge free of charge and returned at the jet bridge on arrival.
This is not a fee situation, but it does mean your bag leaves your possession. Move medication, documents, laptops, chargers and anything valuable into your personal item before you board.
22 x 14 x 9 inches including wheels and handles at most US airlines. Southwest is more generous at 24 x 16 x 10. Many European and Asian carriers add a weight limit of 8–10 kg that US carriers generally do not impose, and enforce it more actively at the gate.
Liquids, gels and aerosols in containers of 3.4 oz (100 ml) or less, all fitting inside one quart-sized clear resealable bag, one bag per passenger. The container size is what matters, not how full it is. Medications, baby formula and breast milk are exempt but should be declared at screening.
United Basic Economy on domestic routes, Spirit Go, Frontier Basic, Allegiant standard fares, Volaris Zero, Avianca XS on many routes, and WestJet UltraBasic. On all of these the carry-on is a separate purchase, and buying it at the gate costs far more than buying it at booking.
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