Flying With a Dog on Southwest: The $125 Pet Fare and the Rules

Southwest keeps its pet policy as simple as the rest of its business. Small dogs fly in the cabin, on domestic flights, in a carrier under the seat, and that is the whole of it. There is no option for the hold and no option for international routes, so if your dog is too big for a carrier or your trip leaves the country, you can stop reading and look at another airline. If your dog does fit, Southwest is one of the more affordable and forgiving ways to fly with one. This guide is drawn from Southwest's pet policy and its published list of charges, as they stood in the autumn of 2026.

What Southwest Allows, in Brief

Southwest welcomes small, vaccinated domestic dogs and cats in the cabin on its domestic flights. The Pet Fare is $125 per carrier, each way, on the mainland, which makes a return trip $250 and undercuts Delta, American and United by $50. No pets are carried in the cargo compartment under any circumstances. Space for pets is limited on every flight, the fare is paid at the ticket counter on the day, and unlike most airlines Southwest will refund it if you cancel.

What It Costs

Southwest's list of optional travel charges gives the Pet Fare as $125 per pet carrier on the US mainland, and $35 per carrier on flights between the Hawaiian islands. A great many websites still quote $95, which was the fare some years ago, so do not be surprised at the counter. The charge is per carrier, not per animal, and that matters because of a rule described below that allows two small pets to share.

The fare must be paid with a credit card at the Southwest ticket counter, so you cannot settle it online in advance. The airline's policy states that if you cancel your reservation, the Pet Fare is refundable, which is unusual. Delta, American, United and Frontier all treat their pet fees as non refundable, so for a trip that might change, Southwest carries less risk.

Will Your Dog Fit?

Southwest's policy sets no weight limit. Its test is the carrier: your dog must travel in an appropriate pet carrier that is stowed under the seat in front of you, and must be small enough to stay inside it comfortably for the whole journey. In practice that means the same kind of dog that flies on other airlines, a small terrier, a dachshund, a toy breed or a puppy, typically up to about 15 or 20 lb depending on shape. Pets must be at least eight weeks old and vaccinated.

Each ticketed customer may bring one pet carrier. Here Southwest is more generous than its rivals, because each carrier may hold up to two small cats or two small dogs, provided they are the same species and both fit. For the owner of two tiny dogs that halves the cost, though two animals in one bag for several hours is only kind if they are small, used to each other and used to the carrier. A child travelling alone as an unaccompanied minor cannot bring a pet.

The Carrier and the Rule About Staying in It

The carrier must go under the seat in front of you and stay there for the flight. Southwest publishes its own guidance on acceptable carriers, including the largest size it will accept, and sells a carrier of its own, so check your bag against the airline's current figures before you travel. A soft sided carrier is the sensible choice, because it has a little give and fits under more seats than a rigid one.

Southwest is strict on one point, and it spells it out. Pets, including their heads and tails, must remain inside the carrier at all times in the gate area, during boarding and leaving the aircraft, and throughout the flight. A dog with its head poking out of the top of the bag for a breath of air is breaking the rule, however sweet it looks. The airline says that if you do not follow these requirements your pet may be denied transportation, and gate staff do enforce it.

Behaviour

Southwest is more explicit than most airlines about how a pet must behave. A pet that shows disruptive behaviour may be denied boarding, and the examples it gives include scratching, excessive whining or barking, growling, biting, jumping and lunging, and urinating or defecating in the cabin or gate area. That list is really a description of a frightened dog, and the cure is preparation. A dog that knows its carrier, has had a long walk and a chance to relieve itself before the airport, and has not just eaten a large meal is very unlikely to trouble anyone.

If your dog has never flown, do not let the flight be its first experience of being zipped into a bag in a noisy place. Our guide to training your dog to travel explains how to build that up over a few weeks at home, and it makes the difference between a dog that sleeps through the flight and one that cries from the gate to the baggage hall.

Where Southwest Will Take Your Dog

Pets are accepted on domestic flights only, so a dog cannot come with you on Southwest's routes to Mexico, the Caribbean or Central America. The policy adds that some destination specific rules apply, and the main one is Hawaii. The state is free of rabies and imposes strict import requirements on every arriving dog, including dogs from the mainland, with quarantine for those that do not meet them. Read our guide to taking your dog to Hawaii and check with the airline before you book any flight there with a pet.

Within the mainland, no federal paperwork is needed for a dog travelling with its owner, but a few states have their own requirements, and it is sensible to carry your dog's rabies vaccination certificate wherever you go. Our guide to dog passports, health certificates and microchips explains what applies to travel between states.

If Your Dog Is Too Big

There is no alternative on Southwest. In the airline's own words, no pets are transported in the cargo compartment. If your dog cannot fit in a carrier under the seat, Southwest cannot carry it, and the realistic choices are to drive or to use an airline that still takes dogs in the hold, of which Alaska is the main one in the United States. Our guides to driving with your dog and to flying a dog in the hold set out both options honestly.

Booking and the Day of Travel

Because space for pets is limited, Southwest recommends making a reservation in advance by calling. Do that as soon as you have booked your own seat, and note the name of the person you spoke to. On the day, go to the ticket counter to pay the Pet Fare and have the carrier looked at, and allow extra time, because this cannot be done at a kiosk or on your phone. At security you carry your dog through the metal detector while the empty carrier goes through the X-ray machine, as the TSA requires, so keep a lead on it.

Give your dog a good walk before you leave for the airport and a last visit to a pet relief area before boarding. Feed it lightly some hours ahead, and do not sedate it. Choose a window seat if you can, where the carrier is out of the way of other passengers' feet. For more on carriers, feeding and what a flight is like for a dog, see our complete guide to flying with a dog.

A Closing Thought

For a small dog on a domestic trip, Southwest is hard to beat: $125 each way, a carrier under the seat, room for two tiny companions in one bag, and a refund of the fare if your plans change. Ring to reserve the pet space, check your carrier against the airline's size guide, and keep your dog zipped in, head and tail and all, from the gate at one end to the kerb at the other.