Southwest Air Pet Carrier Rules: Size, Fees & Booking Steps

A Southwest air pet carrier is a soft- or hard-sided pet container that meets Southwest Airlines Co.'s size, ventilation, and stowage rules so a small cat or dog can fly with you in the cabin. As of August 2026, Southwest charges a $125 one-way pet fare on U.S. mainland flights, caps carriers at roughly 18 inches long, and allows pets only on domestic flights in the cabin — never in cargo — according to Southwest Airlines' official pet policy.

What Counts as an Approved Southwest Air Pet Carrier?

Southwest Airlines accepts both soft-sided and hard-sided carriers, provided the carrier is leak-proof, well ventilated, and small enough to fit entirely under the seat in front of you. The airline sells its own branded pet carrier, but you can also bring a comparable carrier from another manufacturer as long as it stays within the published size limits. Southwest states the carrier must be stowed under the seat for the full flight and that your pet must remain inside it at all times in the gate area, during boarding and deplaning, and throughout the flight, per Southwest Airlines' official help center.

Southwest Pet Carrier Size Chart

Source: Southwest Airlines official carrier-requirements page (2026). If your current pet carrier is oversized for these limits, downsizing before booking avoids a gate-side surprise.

How Much Does a Southwest Pet Carrier Cost?

Southwest lists the pet fare on its Optional Travel Charges page as $125 per pet carrier, each way, on U.S. mainland flights, and $35 per pet carrier, each way, on flights between the Hawaiian Islands, according to Southwest Airlines (2026). The fare is paid per carrier, not per animal, so two same-species pets sharing one approved carrier still pay a single fare. Payment is collected at the Southwest ticket counter, not online, and Southwest accepts credit cards for this charge.

How to Book a Pet in a Southwest Air Pet Carrier

1. Check eligibility. Confirm your pet is a small, vaccinated domestic cat or dog at least 8 weeks old, per Southwest's official pet policy.
2. Reserve a spot in advance. Space for pet carriers is limited per flight, so Southwest recommends calling 1-800-I-FLY-SWA (1-800-435-9792) as soon as you book your own ticket.
3. Pack an approved carrier. Use the size chart above; the carrier must be leak-proof and well ventilated.
4. Arrive early and check in at the counter. You must bring your pet to the Southwest ticket counter to pay the pet fare before heading to the gate.
5. Keep your pet in the carrier. The carrier stays closed and stowed under the seat in front of you for the entire flight, including the gate area and boarding.

Which Pets Qualify for the Southwest Pet Program?

Southwest's cabin pet program is limited to small, vaccinated domestic cats and dogs traveling on domestic flights within the United States. Southwest does not operate a cargo-hold pet program, so any animal too large to travel in an approved cabin carrier under the seat cannot fly as checked baggage or cargo with Southwest. This differs from some other U.S. carriers that offer separate cargo pet-shipping services.

Tips for Choosing a Southwest-Approved Pet Carrier

Because the carrier must be stowed under the seat in front of you for the entire flight, measure the actual usable space before you buy or pack, not just the advertised seat pitch — tray tables, seatback pockets, and the metal support bar under some rows can shrink the available height. A soft-sided carrier with mesh panels tends to compress slightly to clear tight under-seat spaces, while a rigid hard-sided carrier holds its exact dimensions and leaves no margin for error.

• Measure before you fly. Compare your carrier's actual footprint against the chart above, not just the manufacturer's size label.
• Check ventilation on all sides. Southwest requires the carrier to be well ventilated, so mesh panels on at least two sides help keep your pet comfortable during boarding delays.
• Practice a trial fit at home. Set the carrier on the floor and use a dining chair to simulate the seat in front of you, confirming it slides underneath without force.
• Leave a paper trail. Bring proof of vaccination in case ground staff ask, since Southwest's policy specifies only vaccinated cats and dogs may travel.
• Call before you pack. Because pet-carrier space is limited per flight, confirm your reservation is still active a day or two before departure.

What Southwest's Pet Carrier Policy Does Not Cover

International flights

Southwest's official pet policy describes cabin pet travel for domestic flights; it does not extend the paid pet-carrier program to international routes. If you need to fly a pet abroad, you'll need to work with an airline and government agency that supports international pet entry requirements for your destination.

Emotional support animals

Effective March 1, 2021, Southwest Airlines revised its policy to accept only trained service dogs individually trained to perform tasks for a person with a disability, in line with U.S. Department of Transportation rules, and stopped transporting emotional support animals, per Southwest Airlines' investor press release. Customers traveling with an emotional support animal must instead book it into the standard paid pet-carrier program described above, subject to carrier size and species limits.

Service animals

Trained service dogs travel free of the pet fare and are not required to use a pet carrier, but customers must present a completed U.S. Department of Transportation Service Animal Air Transportation Form at the gate or ticket counter.

Southwest Pet Carrier vs. an Official Pet Travel Document

A pet carrier and a pet passport solve two different problems, and travelers often conflate them. A Southwest air pet carrier is a piece of physical equipment that must meet size and ventilation rules for a domestic U.S. flight. A pet passport, by contrast, is an official identification and health-record document. The European Commission's Your Europe portal describes the EU pet passport as an identification document that follows an EU standard model, issued by an authorized veterinarian for a dog, cat, or ferret, and required for that pet to cross borders between European Union member states. It records the animal's microchip number, rabies vaccination history, and owner and vet contact details, and is recognized across the EU plus Iceland, Norway, Switzerland, and other participating countries. Southwest does not issue or recognize EU pet passports, and holding one does not change Southwest's U.S. domestic-only cabin carrier rules.

This is also where digital identity tools for animals are evolving outside the airline-carrier context entirely. Animal Passport is a phone-based digital identity record that uses muzzle biometrics — a nose print unique to each animal, similar to a human fingerprint — to bind an owner, breed, estimated age, body condition score, and vaccination history to a specific animal. It was used during livestock flood rescue efforts in Pakistan in August 2025, helping farmers reclaim animals after paper ear tags washed away. That is a livestock identification tool, not an airline travel document and not a substitute for an EU pet passport or a Southwest-approved carrier — the three serve entirely different purposes and audiences. Readers researching digital animal identification more broadly can see more use cases on the Animal Passport blog.

Frequently Asked Questions

What size pet carrier does Southwest Airlines allow?

Southwest's own branded carrier measures 15" L x 10" W x 10" H, and other soft- or hard-sided carriers may measure up to 18" L x 10.5" W x 10" H, as long as the carrier fits fully under the seat in front of you, per Southwest Airlines' official carrier-requirements page.

How much does it cost to bring a pet on Southwest Airlines?

Southwest charges a $125 pet fare each way per carrier on U.S. mainland flights, and $35 each way between the Hawaiian Islands, according to Southwest's Optional Travel Charges page (2026).

Can two pets share one carrier on Southwest?

Yes. Southwest allows up to two small cats or dogs of the same species in a single approved carrier, and that carrier counts as your one carry-on or personal item.

Does Southwest allow pets on international flights?

Southwest's published pet policy covers cabin travel on domestic flights; it does not describe pet-carrier service on international routes, so international pet travel is not available through Southwest's standard pet program.

Does Southwest still allow emotional support animals?

No. Since March 1, 2021, Southwest accepts only trained service dogs performing tasks for a person with a disability; emotional support animals must travel under the standard paid pet-carrier program instead.

Do I need to book my pet's seat in advance?

Yes. Southwest recommends calling 1-800-I-FLY-SWA in advance because space for pet carriers on each flight is limited, and the pet fare is paid at the ticket counter, not at booking.

Is a Southwest pet carrier the same as an EU pet passport?

No. A Southwest pet carrier is physical equipment that meets U.S. domestic cabin-stowage rules, while an EU pet passport is an official veterinary identification and health document required to move a dog, cat, or ferret between EU member states, per the European Commission.

How old does a pet need to be to fly on Southwest?

Pets must be at least 8 weeks old to travel in Southwest's cabin pet program, per Southwest Airlines' official pet policy.