"Airline-Approved" Pet Carriers (2026): Under-Seat Sizes by Airline, and the Carriers That Fit

No carrier is approved by every airline, because each airline sets its own under-seat limit and the space varies by aircraft. What you can do is compare a carrier's listed size to the numbers your airline publishes. On paper, the Petmate Kennel Cab fits four of the six US airlines we checked; the Mr. Peanut's Gold Series Standard and Sherpa Original Deluxe Medium fit American, Delta and United.

How we chose: we did not test these carriers; we loaded each airline's own pet page on September 28, 2026, compared its limits to each carrier's listed dimensions, and kept only carriers sold by Amazon.com or the brand's own store and in stock that day.

What each airline allows under the seat

All figures are in inches, as each airline states them on its pet page, checked September 28, 2026. Airlines change these pages, so check yours before you book.

A few rules on those pages matter as much as the size:

• American says soft-sided carriers are recommended and "can be slightly larger but still need to fit under the seat without having to excessively collapse the kennel." They must have mesh ventilation on three or more sides. On the three-cabin A321T, pet plus carrier must not exceed 20 lb.
• Delta says the maximum "is determined by the aircraft dimensions of your flight" and recommends 18 x 11 x 11 in because "this fits most aircraft types." One pet per kennel, with exceptions for young litters.
• United caps carrier height at 10 in on the Boeing 737 MAX, and on some planes you must sit in a window or aisle seat for the carrier to fit.
• Southwest allows up to two small cats or dogs of the same species in one carrier, and warns that under-seat space varies by seat type, "including aisle seats."
• Alaska allows up to two pets of the same species and similar size per carrier, and does not allow hard-sided kennels in the cabin.
• JetBlue allows one pet per carrier, and the pet and carrier count as your personal item.

Which carriers fit which airline, on paper

This compares each carrier's listed length, width and height to the airline's published soft-carrier size. A "No" means at least one dimension is over the limit before any compression.

Prices are Amazon's, as of the time shown, and subject to change. Details

Key point: "Airline approved" on a listing is the brand's wording. None of these six airlines names or approves carrier brands on its pet page; each publishes a size and leaves the gate agent to judge whether your carrier fits under the seat.

That is also why soft carriers exist. Sherpa says the Original Deluxe's spring wire frame lets the rear "be pushed down several inches" to fit under a seat. SturdiBag describes its soft-sided carriers as "flex-height" on its listings, and Mr. Peanut's says its carriers are designed for pets lying down. A carrier a little over on paper may still go under the seat, but the airline decides at the gate, and a pet squashed by a compressed top is not riding comfortably.

For the most airlines: Petmate Kennel Cab

At 17 x 10 x 10 in per the listing, the Petmate Kennel Cab is the only pick within American's, Delta's, United's and Southwest's published soft-carrier sizes, and it stays under United's 10 in height on the 737 MAX. It has a top-loading zippered door, mesh walls and a pad. Petmate rates it for pets up to 10 lb, so it suits a cat or a very small dog.

For more room on the big three: Mr. Peanut's or Sherpa

The Mr. Peanut's Gold Series Standard lists 18 x 11 x 10 in, inside the 18 x 11 x 11 in size American, Delta and United use, and 10 in tall for the 737 MAX. Mr. Peanut's says it best fits pets up to about 16 in long lying down and up to 15 lb, and its title describes it as expandable.

The Sherpa Original Deluxe Medium lists 17 x 11 x 10.5 in, so it fits the same three airlines, except United's 737 MAX on paper. Its top and side openings make it easy to load a reluctant cat.

SturdiBag: extra room, if the top compresses

Both SturdiBag Pro 3.0 sizes are over the common 18 x 11 x 11 in size on paper: the Large by half an inch in width and height, the Medium by an inch in width. SturdiBag's pitch is that the soft top gives, so the height flexes to fit under a seat. SturdiBag also notes that its XL and XXL sizes "are not airline-compliant," which is why we list only the Medium and Large. Buy one if your pet needs the room and you are ready to show the gate agent how it compresses.

Before you book: health, sedation and international trips

Book your pet with the airline early. Every airline above limits the number of pets per flight, and some limit it per cabin.

Do not plan on sedating your pet. American says that, "as recommended by the American Veterinary Medical Association (AVMA)," it does not accept sedated or tranquilized pets, because they are "at a higher risk of respiratory and cardiovascular problems at high altitudes." If your pet is anxious about travel, ask your vet what is safe. This page is not veterinary advice (more on that).

For trips abroad, the USDA APHIS pet travel page says to contact a USDA-accredited veterinarian as soon as you decide to travel. They will help you work out the destination country's entry rules and get a USDA-endorsed health certificate. For dogs coming back into the US, APHIS notes that the CDC is "the primary authority for dog imports." Several airlines also bar in-cabin pets to certain destinations; Alaska, for example, lists all of Europe and Japan.

Once you land, a travel carrier is not a crash restraint in a car. Of the carriers on this page, none is on the Center for Pet Safety certified list. If your carrier will ride in a car often, read our guide to crash-tested dog car harnesses, carriers and crates. For the walk from the car to the terminal, see our picks for no-pull dog harnesses.

The carrier we left out

The Sleepypod Air is on the Center for Pet Safety certified list as a carrier, tested in January 2025 with an 18 lb test dog. On Amazon, though, it was sold only by a third-party seller when we checked, so it did not meet our seller rule. Sleepypod sells it on its own site.

We found no CPSC recall of these carriers in the CPSC recall database. Petmate had a 2025 CPSC recall of Pet Zone toys, which does not involve carriers. Check any brand on our pet product recall page.

Frequently Asked Questions

Is there a carrier that is approved by all airlines?

No. Airlines publish a size limit rather than approving brands, and the limits differ: of the six we checked, Alaska and JetBlue have the smallest. A carrier within the size you are flying, that still lets your pet turn around, is what the airline checks.

What size pet carrier fits under an airline seat?

18 x 11 x 11 in is the soft-carrier size American, Delta and United publish or recommend. Southwest's is 18 x 10.5 x 10 in, Alaska's 17 x 11 x 9.5 in and JetBlue's 17 x 12.5 x 8.5 in, all checked September 28, 2026.

Soft-sided or hard-sided carrier for a flight?

Soft-sided. American and Delta both recommend soft-sided carriers, and Alaska does not allow hard-sided kennels in the cabin at all.

Can two pets share one carrier?

On some airlines. Southwest and Alaska allow two pets of the same species in one carrier; JetBlue allows one per carrier; Delta allows two only for young pets of the same breed and size.

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PetProofLab is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com. We did not test these carriers; sizes are from the listings, and airline rules change, so check yours before you fly.