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Short answer: a soft-sided carrier around 18 × 11 × 11 inches fits what Delta, American and United recommend. Alaska (17 × 11 × 9.5 soft) and JetBlue (17 × 12.5 × 8.5) allow less, so a carrier that’s fine on Delta can be too tall for them. Measure the outside of your carrier, check it below for your airline, and book your pet’s spot early: cabins take only a few pets per flight, and Thanksgiving flights fill first.
A note from Helen: Teya, our small Pomeranian, travels with us a lot, and when she flies she goes in her carrier. The worry is always the same: will the carrier pass at the gate? This guide uses the limits on the airlines’ own pages where we could reach them, checked October 29, 2026, and a published summary of United’s rules. Rules change, so confirm with your airline when you book.
Carrier size checker
Does your carrier fit?
Enter the outside size of your carrier in inches. Nothing you type leaves your browser.
“Squeeze” means a soft carrier is up to an inch over in one direction. Airlines say soft carriers can flex to fit, but they must go fully under the seat without being crushed flat, so measure your pet inside it too.
Airline limits side by side
Inches, length × width × height:
| Airline | Soft-sided | Hard-sided | In-cabin fee (each way, US) |
|---|---|---|---|
| Delta | 18 × 11 × 11 (recommended) | Must fit under the seat; varies by aircraft | $150 |
| American | 18 × 11 × 11 | 19 × 13 × 9 (American Eagle: 16 × 12 × 8) | $150 |
| United | 18 × 11 × 11 (recommended) | 17.5 × 12 × 7.5 | Check when booking |
| Alaska | 17 × 11 × 9.5 | 17 × 11 × 7.5 | $100 |
| JetBlue | 17 × 12.5 × 8.5 (any carrier) | Check when booking | |
Two things stand out. First, height is where most carriers fail: an 11-inch-tall carrier is fine on Delta but too tall for Alaska and JetBlue. Second, regional jets have less space: American lists a smaller hard-carrier limit for American Eagle flights, and Delta says space varies by aircraft. If your trip has a small-plane leg, a soft carrier is the safer bet. Southwest also carries pets in the cabin, but published summaries of its size limit disagree, so check southwest.com before you buy a carrier for it.
How to measure a carrier
- Zip every pocket and empty the carrier.
- Measure the outside: length (the longest side), width and height, including the frame, feet and any handles that stick out.
- Soft carriers with expandable sides: measure with the extensions zipped closed. Expand them only at your seat if the airline allows.
- Check your pet fits inside: your dog or cat must be able to stand up and turn around with the carrier closed.
That last rule is where small dogs can be trickier than cats: a Pomeranian looks bigger than she is because of the fluff, but a long-backed dog may need more length than its weight suggests. Measure your pet nose to the base of the tail and from the floor to the top of the head while standing, and compare with the inside of the carrier.
Soft or hard carrier?
For the cabin, soft. Delta recommends soft-sided kennels, American says soft carriers are recommended and can be slightly larger than its hard-sided limit as long as they fit under the seat without being forced flat, and United gives a recommendation for soft carriers rather than a hard limit. Hard carriers make sense in the car or for cargo, not under a seat. For a big cat who won’t fit any cabin carrier, read our hard vs soft carrier guide for big cats.
Booking and fees
- Book the pet when you book your seat. Airlines limit pets per cabin: Delta allows 4 in Main Cabin and Comfort and 2 in domestic First. On busy holiday flights the spots go early.
- Fees are per carrier, each way: $150 on Delta and American for US domestic flights, $100 on Alaska, as listed on their pages on October 29, 2026.
- Your carrier usually replaces a bag. American allows the carrier plus either a personal item or a carry-on, not both.
- Seat rules: no bulkhead or exit rows, and some premium seats are excluded.
- Age: Delta requires pets to be at least 8 weeks old for domestic travel.
- Hawaii and the UK are among destinations where Delta doesn’t take pets in the cabin.
On the day: checklist
Driving to Thanksgiving instead? See car seat vs carrier vs harness for small dogs, and before the big dinner, the list of Thanksgiving foods that are dangerous for dogs and cats.
Carriers worth a look
Affiliate note: some links in this guide go to Amazon. As an Amazon Associate we earn from qualifying purchases, at no extra cost to you. We haven’t tested these carriers on flights; check each listing’s exact outside size against the checker above, because most come in more than one size.
Classic soft carrier: Sherpa Original Deluxe
One of the best-known airline carriers: soft sides, mesh ventilation and a shoulder strap. It comes in several sizes, so pick the one whose height fits your airline.
Check the size label: the larger sizes are too tall for Alaska and JetBlue.
See sizes on AmazonFlexible sides: SturdiBag
A soft carrier with flexible sides and top designed to compress a little under the seat while keeping its shape around your pet.
Check your airline’s height limit before buying the larger size.
See sizes on AmazonThe small extras
- A collapsible water bowl
- Small puppy pads for the carrier floor
- A luggage tag with your phone number
Frequently asked questions
What size pet carrier fits under an airplane seat?
A soft-sided carrier no bigger than about 18 x 11 x 11 inches fits the recommendation of Delta, American and United. Alaska (17 x 11 x 9.5 soft) and JetBlue (17 x 12.5 x 8.5) are smaller, so check your airline before you buy.
Are soft or hard pet carriers better for flying?
Soft-sided carriers. Airlines recommend them because they can flex a little to fit under the seat. American says a soft carrier may be slightly larger than its hard-sided limit as long as it fits without being forced flat.
How much does it cost to fly with a pet in the cabin?
As of October 2026, Delta and American charge $150 each way on US domestic flights and Alaska charges $100. Fees are per carrier and paid at check-in.
Does my pet count as my carry-on?
Usually yes. On American, for example, you can bring the pet carrier plus either a personal item or a carry-on bag, not both. Check your airline's rule.
Can I sedate my dog for a flight?
American doesn't accept sedated or tranquilized pets, and vets generally advise against sedation for flying. Ask your vet about other ways to keep your pet calm.
How do I measure a pet carrier?
Measure the outside of the carrier with the pockets zipped and nothing inside: length (longest side), width and height. Include any frame or feet.
