Airline Under-Seat Pet Carrier Dimensions (2026)

Every US airline publishes a maximum in-cabin carrier size, and they mostly agree on the footprint — around 18 x 11 inches — and disagree on the height. That height number is what gets a carrier rejected at the gate, so it's the column to read first. Figures below were checked on 22 July 2026. Airlines change these without much notice — treat this as your shortlist, then confirm on the airline's own page before you fly.

Airline	Max soft carrier (L×W×H, in)	In-cabin fee (each way)	Key rule
United	18 × 11 × 11	$150	No stated weight limit; must fit and turn under the seat
Delta	18 × 11 × 11 (recommended)	$150 (US) / $200 intl	Must fit fully under the seat; ventilation on 3+ sides
American	18 × 11 × 11	$150	Pet + carrier ≤ 20 lb; must stand, turn, lie down
Southwest	18.5 × 13.5 × 8.5	$125	Pet + carrier ~20 lb; low height limit
JetBlue	17 × 12.5 × 8.5	$125	Pet + carrier ≤ 20 lb; small dogs/cats only
Alaska	17 × 11 × 9.5	$100	Pet stays in carrier gate-to-seat
Frontier	18 × 14 × 11	$99	Must fit under the seat
Spirit	18 × 14 × 9	$125	Must fit under the seat

Verified 22 July 2026 against each airline's published pet policy. Delta's figures and Southwest's fee and JetBlue's dimensions were read on the airline's own site; United, American, Alaska, Frontier and Spirit figures are cross-checked from the airlines' published policies via reputable secondary sources because those sites block automated access — confirm them on the airline page before you travel. Sources are listed at the foot of this page.

How to use this table

Read the height column first

The footprint (length × width) is nearly the same everywhere. The height is where airlines split: 11 inches on United, Delta and American; about 8.5 on Southwest and JetBlue. A carrier bought for a United flight can be rejected on a Southwest one for that reason alone. If you fly several airlines, buy to the lowestheight you'll face, not the average.

Soft carriers buy you an inch, not four

A soft-sided carrier flexes under the seat, so being an inch over the stated height is usually survivable — that flex is the reason we recommend soft carriers for the cabin. But it is not a license to ignore the number. Two or more inches over and you're gambling with the gate agent.

The dog has to fit the carrier, too

A carrier that clears the seat is useless if the dog can't stand and turn inside it — airlines check that, and it's the humane minimum anyway. That's the squeeze: small enough for the seat, big enough for the dog. If your dog can't satisfy both, it may be too big to fly in cabin on that airline. Measure first with our measuring guide, then shop the carrier roundup.

Fees are per direction, per pet

The fee columns are each way. A round trip is double, and a second pet is another fee (where allowed at all). Budget it in — at $100–$200 each way, the fee often costs more than the carrier.

Questions

Frequently asked

What is the standard under-seat carrier size for airlines?

Most US airlines allow a footprint around 18 x 11 inches. The height is where they differ: roughly 11 inches on United, Delta and American, but only about 8.5 inches on Southwest and JetBlue. Because a soft carrier flexes, aim for a carrier no taller than your strictest airline's limit.

Which airline has the strictest carrier height limit?

Among major US carriers, Southwest and JetBlue are the strictest on height at around 8.5 inches, versus about 11 inches on United, Delta and American. If you fly a mix, buy to the lowest height you'll encounter — a taller carrier that's fine on one airline gets rejected on another.

How much does it cost to fly with a dog in the cabin?

For major US airlines, roughly $99 to $150 each way as of July 2026 (Alaska is around $100, United/Delta/American around $150, Southwest/JetBlue/Spirit around $125, Frontier around $99). That's per direction and per pet, so a round trip is roughly double. Confirm the current fee on the airline's page — they change.

Do these dimensions change?

Yes — airlines update carrier limits and fees without much notice, and aircraft type can change the under-seat space on a given flight. Use this table to shortlist, and always confirm the current numbers on your airline's own pet-policy page before you buy a carrier or book.

Keep reading

Receipts

Sources

We do not run a testing lab, and we do not pretend to. Product dimensions and safety claims come from the manufacturer's own listing; airline limits come from the airline's published policy, with the date we checked it. Where we could not verify something, we say so on the page rather than quietly leaving it out. Read our full method.