US carry-on rules: airline limits and TSA security
Your airline sets the size and cost of your carry-on. TSA sets what can go through security. Here is how both work.
Two sets of rules apply to a US carry-on
Flying in the United States, your carry-on is governed twice. Your airline decides how big your bags can be and whether you pay. TSA decides what is allowed through the security checkpoint. A bag can pass one and fail the other.
1. Your airline: size and cost
Most big US airlines list a carry-on of 22 x 14 x 9 inches (about 56 x 36 x 23 cm) including handles and wheels, plus a smaller personal item that goes under the seat. Southwest and Frontier list 24 x 16 x 10 inches. The carry-on is free on the big airlines but a paid add-on on Frontier, Sun Country, Breeze and Avelo. See every airline in one size table.
2. TSA: what goes through security
- Liquids: containers of 3.4 ounces (100 ml) or less, all in a quart-sized bag.
- Food: solid food is fine; liquid and gel foods over 3.4 ounces are not.
- Baby formula and breast milk: allowed in quantities over 3.4 ounces, declared at the start.
- Power banks: carry-on only, never checked, and some airlines add limits of their own.
TSA states that the final decision on whether an item is allowed rests with the TSA officer at the checkpoint (TSA "What Can I Bring?" pages, read 5 November 2026). For an item no page covers, TSA says to contact AskTSA.
If your carry-on does not fit or the bins are full
- Sun Country: if a bag you pre-purchased does not fit its sizer box at the gate, it is checked and extra charges may apply. If the bins fill up, remaining overhead bags are tagged and travel as checked bags.
- Frontier: if there is no overhead space, a bag may be gate-checked at no additional cost.
- The FAA requires that when a carry-on is checked at the gate, all spare lithium batteries and power banks are removed and kept with you in the cabin.
Sources: Sun Country bags, FAA PackSafe lithium batteries, TSA liquids rule, TSA food list, and the airline pages linked from the size table. Checked 5 November 2026.
Frequently asked questions
What are the carry-on rules in the US?
There are two sets. Your airline sets the size and cost of your carry-on and personal item. TSA sets what may pass through security, including the 3.4 ounce (100 ml) limit on liquids, aerosols, gels, creams and pastes.
Is hand luggage the same as carry-on?
Yes. Hand luggage, cabin baggage and carry-on all mean the bag you take into the cabin. Americans usually say carry-on and personal item.
How many bags can I bring on a US flight?
Most airlines allow one carry-on bag and one personal item. On Frontier, Sun Country, Breeze and Avelo the carry-on is a paid add-on, so the free allowance is the personal item only.
Does TSA decide my carry-on size?
No. Size limits come from the airline. TSA screens what is inside your bags; it does not publish a carry-on size limit on the pages we read.
Can I take a power bank on a US flight?
Yes, in your carry-on only. Spare lithium batteries and power banks are not allowed in checked bags. Delta, Southwest and American have their own limits as well; see our power bank page.