United Airlines Pet Carrier Guidelines: 2026 Carrier Sizes, Fees and Cabin Rules

United Airlines pet carrier guidelines are the rules United sets for carrying a cat or dog in the passenger cabin. As of September 2026, your pet must ride in a ventilated soft-sided carrier no larger than 18 x 11 x 11 inches, or a hard-sided kennel no larger than 17.5 x 12 x 9 inches. The carrier has to fit completely under the seat in front of you, and on Boeing 737 MAX aircraft it can be no more than 10 inches tall. The fee is $150 each way.

This guide, last updated on 27 September 2026, walks through every carrier dimension, the aircraft and seat exceptions, the paperwork U.S. agencies require for international trips, and where sources disagree. We also explain why an airline pet ticket is a completely different thing from the biometric livestock record that Animal Passport builds.

What are United Airlines' pet carrier size limits?

United publishes two maximum sizes, one for each type of carrier. Both independent trackers we checked in 2026, LegalClarity (published June 2026) and CabinPets (last verified 23 September 2026), report the same figures from United's Traveling with Pets policy:

A few practical notes on reading those numbers:

• Measure the outside of the carrier, including pockets, bulges and handles. CabinPets checks height strictly and lets the footprint rotate, which matches how gate agents usually measure.
• Your pet must be able to stand up and turn around comfortably inside the carrier. United's own pet acknowledgement makes this a condition of travel, so a large dog that only fits by being squeezed in is effectively too big, even though there is no weight limit.
• Soft-sided is usually the safer choice. LegalClarity (2026) notes that fabric carriers compress slightly under tighter seats, while a rigid kennel that is even slightly oversize simply will not fit.

The Boeing 737 MAX 10-inch rule

The most common reason travelers get stopped at the gate is the Boeing 737 MAX height cap. According to CabinPets (2026), which cites a footnote on United's policy page, carriers on the 737 MAX can be no more than 10 inches tall. Travel With Cats (March 2026) describes a passenger at Chicago O'Hare whose 11-inch soft carrier was tape-measured at check-in and flagged as an inch too tall for the MAX flight. Check the aircraft type in your booking before you fly. If any leg is a 737-8 (MAX 8) or 737-9 (MAX 9), choose a carrier that is 10 inches tall or less.

Where sources disagree on hard-sided height

Most 2026 summaries of United's main pet policy give 9 inches as the hard-sided height limit. However, the in-cabin pet acknowledgement text on a United account-profile page, as indexed by search engines in September 2026, lists a lower hard-sided height of 7.5 inches (19.05 cm). We could not settle which figure United enforces at the gate. If you plan to use a hard-sided kennel between 7.5 and 9 inches tall, call United to confirm, or use a soft-sided carrier, whose 18 x 11 x 11 inch limit is the same in every source.

How much does United charge to fly a pet in the cabin?

United charges $150 each way per pet for in-cabin travel, according to LegalClarity (2026), CabinPets (2026) and Travel With Cats (2026). Travel With Cats also notes that Delta Air Lines and American Airlines charge the same $150 each way in 2026. If you bring two pets, you pay two pet fees ($300 each direction) plus the price of a second, adjacent seat.

Which pets can fly and how many per passenger?

Only cats and dogs are accepted as in-cabin pets on United. Rabbits, birds, ferrets and other species are not. United sets no weight or breed limit, so the carrier size is the only physical limit (LegalClarity, 2026).

• Minimum age: 2 months for domestic flights. For international flights, sources give different minimums. LegalClarity (2026) says 4 months for pets in general. Travel With Cats (2026) says 4 months for kittens and 6 months for dogs, because the CDC requires dogs to be at least 6 months old when they enter the United States.
• Pets per person: up to 2 on most flights, and the second pet needs its own purchased seat next to yours.
• One-pet aircraft: on the Airbus A319, A320 and A321neo and the Boeing 737-800, 737-8 (MAX 8), 737-900 and 737-9 (MAX 9), the space under middle seats is limited, so United allows only one pet per person (CabinPets, 2026).
• Per-flight caps: Travel With Cats (2026) reports up to 4 pets in economy on most narrowbody aircraft, 3 on the Embraer 175, 6 on the Boeing 767, 777 and 787, and up to 2 in United First on eligible aircraft. Spots are first-come, first-served.

Where can't you sit with a pet on United?

Because the carrier has to go under the seat in front of you and cannot block an evacuation route, several seats are off-limits. According to CabinPets and LegalClarity (2026), these are:

• Emergency exit rows
• United Premium Plus seats
• The front (bulkhead) row of any cabin, which has no under-seat storage

Travel With Cats (2026) adds that United Polaris business class does not list any pet spots. These rules cover flights operated by United. For United Express or partner airline flights, confirm with the airline actually operating the flight.

How to book and check in a pet on United: step by step

1. Check the aircraft type for every leg of your trip. It decides whether the 10-inch MAX height rule and the one-pet limit apply.
2. Confirm your route is allowed. United bans in-cabin pets on flights to, from or through Hawaii and a list of countries (see below).
3. Add the pet on united.com. Select "Travel with a pet" as a traveler when you book, or add it later in My Trips. You cannot add a pet in the United app, and LegalClarity (2026) reports that international pet bookings must be made by phone.
4. Buy a carrier that fits the limits in the table above, and get your pet used to spending time in it.
5. Prepare documents if you are flying internationally (see the next section).
6. Check in at a kiosk. For domestic flights, the kiosk prints a pet tag for the carrier (CabinPets, 2026).
7. Clear security. Take your pet out of the carrier, carry it through the metal detector, and send the empty carrier through the X-ray machine (LegalClarity, 2026).
8. Keep the carrier closed under the seat in front of you for the whole time you are in the airport and on the plane.

Which routes ban in-cabin pets on United?

United does not accept in-cabin pets on flights to, from or through a list of destinations. Travel With Cats (checked against United's page in May 2026) lists Australia, Barbados, Brazil, Cuba, Dominica, the Dominican Republic, French Polynesia, Greenland, Guam (with exceptions), Guyana, Hawaii, Hong Kong, Iceland, Ireland, Jamaica, the Marshall Islands, Micronesia, Mongolia, Morocco, New Zealand, the Northern Mariana Islands, Palau, the Philippines, Saint Kitts and Nevis, South Africa, Spain (Bilbao only), Sweden, Taiwan (with exceptions), Thailand, Trinidad and Tobago, the United Arab Emirates, the United Kingdom and Vietnam. The ban applies even if you are only connecting through one of these places, so check the list on united.com before you book, because it changes.

United has also ended its PetSafe cargo program for civilian travelers. In 2026, pets fly in the hold only with certain active-duty U.S. military personnel or U.S. State Department employees (CabinPets; Travel With Cats, 2026). Other travelers who need cargo transport generally use a pet relocation company.

What documents do you need for international flights?

United requires a health certificate and proof of rabies vaccination for pets on its international flights. LegalClarity (2026) reports that the rabies shot must be given at least 28 days before departure. United does not run these government rules itself, so check the agencies below.

Leaving the United States

The United States Department of Agriculture Animal and Plant Health Inspection Service (USDA APHIS) advises owners to contact a USDA-accredited veterinarian as soon as they decide to travel. That vet checks the destination country's rules and submits the health certificate for USDA endorsement (APHIS export page, last modified 14 August 2026). APHIS also warns that destination-country requirements "can change at any time" and should be checked for every trip.

Bringing a dog into (or back to) the United States

The U.S. Centers for Disease Control and Prevention (CDC) is the main federal authority for dog imports. Since 1 August 2024, dogs that have been only in dog-rabies-free or low-risk countries for the previous 6 months need just the free CDC Dog Import Form. They must also be at least 6 months old, look healthy, and have a microchip that a universal scanner can read (CDC, 2024). Dogs that have been in a high-risk country need more paperwork. According to APHIS (2026), U.S.-vaccinated dogs in that situation need a "Certification of U.S.-Issued Rabies Vaccination" form, completed by a USDA-accredited vet before the dog leaves the country. The form cannot be issued after the dog has left.

Common mistakes that get pets turned away

• Relying on an "airline-approved" label. CabinPets (2026) found that only 9 of the 15 popular carriers it tracks fit United's 18 x 11 x 11 inch limit, and many that do are exactly 11 inches tall, which is too tall for a 737 MAX.
• Booking two pets on a narrowbody plane. Most domestic United flights use aircraft on the one-pet list.
• Assuming Hawaii counts as a normal domestic trip. It is on the banned list.
• Treating an emotional support animal as a service animal. LegalClarity (2026) reports that United counts emotional support animals as pets, so they need a carrier and the $150 fee. Only trained service dogs fly free without a carrier.

Airline pet rules vs. Animal Passport: not the same thing

People often mix up the documents in this area, so here is the difference. United's pet carrier guidelines, USDA-endorsed health certificates and the CDC Dog Import Form are the official requirements for flying with a cat or dog. Animal Passport is not one of those documents. It is not issued by a government, United does not accept it for travel, and it does not replace a veterinary health certificate.

Animal Passport is a digital animal and livestock passport built on muzzle biometrics: an animal's nose print is unique, like a fingerprint. A farmer captures it with a phone, and the record links the animal to its owner, breed, estimated age, body condition and vaccination history. Age is estimated from a dental photograph and comes with a confidence score, and body condition is scored from 1 to 5 using a side-profile photo. In August 2025, the system was used in livestock flood rescue in Pakistan, so farmers could reclaim animals after paper tags washed away.

The line between the two matters in U.S. rules too. USDA APHIS (2026) states that animals considered livestock or poultry, such as pigs or chickens, do not qualify for pet travel and fall under separate import and export regulations. In other words, airline pet rules are for companion cats and dogs, while livestock identity is a separate problem. For more on biometric livestock ID, see the Animal Passport blog.

Bottom line

As of September 2026, the safe way to meet United Airlines pet carrier guidelines is a soft-sided carrier no more than 18 x 11 inches in footprint and no more than 10 inches tall. That size clears both the standard limit and the Boeing 737 MAX cap. Add the pet to your booking early, check the aircraft type and banned-route list, and budget $150 each way. For international trips, start the USDA APHIS and CDC paperwork weeks ahead. Always recheck United's own pet page before you fly, because airline policies change without notice.