Flying Southwest Airlines with a Cat (2026): No Weight Cap, Two Cats Per Carrier — and the Booking Step That Fills Up Fast

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Southwest allows cats in the cabin on domestic US mainland flights. The fee is $125 per carrier, one-way, for as many as two cats travelling in the same carrier. Policy verified directly from southwest.com and Southwest's Optional Travel Charges page, May 2026.

Travel with Cats covers every major airline's pet policy with direct verification from the source, not aggregated summaries. What you'll find here: what actually distinguishes Southwest from Delta, United, and American Airlines — not just a repeat of the policy page — and the specific steps that trip people up when booking.

Southwest cat policy at a glance

Before getting into what makes Southwest different, here is the full policy in one place.

Southwest reserves the right to change pet fares at any time. Confirm directly before booking.

What Southwest's policy doesn't tell you — and what actually matters when you are planning a trip with your cat — is covered below.

What makes Southwest different from Delta, United, and American Airlines

No weight limit — just the carrier dimensions

Delta and American Airlines each charge $150 per kennel one-way for in-cabin cats — $25 more per carrier than Southwest's $125 fee. United also allows cats in the cabin and currently lists pet tickets at $150 each way. The key difference with Southwest beyond price is that there is no stated weight limit at all. The policy requires only that the cat fits comfortably inside a carrier that slides under the seat in front of you and that the cat can stand up and move around with ease. Southwest does not publish a combined cat-plus-carrier weight limit.

This matters for owners of larger domestic cats — a Maine Coon or Norwegian Forest Cat that might exceed the 8 kg combined-weight cap imposed by European carriers like KLM or Lufthansa is not automatically ruled out on Southwest, provided it fits comfortably in an approved carrier.

That said, "fits comfortably" is assessed by Southwest staff at the airport, not by you at home. If your cat is visibly cramped or cannot stand, the carrier can be refused. The welfare test is real, even if the weight limit is not.

Two cats in one carrier — the rule most readers miss

This is the detail that changes the economics for multi-cat households. Southwest allows up to two cats of the same species in a single carrier — and charges one $125 fee for that carrier. For most adult-cat trips, Delta and American are less favourable for two-cat travel because they generally price by kennel and restrict how many pets can share one carrier — check each airline's age and same-carrier exceptions before booking. On Southwest, both cats travel together in one carrier for $125.

The conditions: both cats must be the same species (cats with cats, not cats with dogs), both must fit comfortably in the carrier, and both must be able to stand and move around inside. Southwest staff will assess this at check-in. If the carrier is clearly overcrowded, it will not be accepted.

In practice, two small cats in a soft-sided carrier that meets the size requirements is a standard and accepted scenario on Southwest. Across multiple accounts from FlyerTalk and pet travel communities, this is noted as one of Southwest's genuine practical advantages over the other major US carriers.

A simpler fleet means fewer complications

Delta and United operate wide-body aircraft (Boeing 777, 787, Airbus 330) on routes where carry-on space under First and Business Class seats does not exist — meaning pets can be prohibited from premium cabins on those routes. American Airlines operates similar wide-body aircraft with corresponding restrictions.

Southwest operates an all-Boeing 737 fleet. There are no wide-body aircraft, no First Class cabin, and no regional jet subsidiaries operating under the Southwest brand with different carrier size limits. The size requirement is the size requirement, on every Southwest aircraft, on every domestic route. If your carrier fits, it flies.

This fleet consistency simplifies the carrier-buying decision. You do not need to check whether the aircraft on your specific route is a regional jet with a smaller underfloor clearance. One compliant carrier works everywhere Southwest flies.

The pet fare is refundable

If you cancel your reservation, Southwest refunds the $125 pet fare. This is not universal among US carriers — confirm your carrier's refund policy before booking. The refund applies when you cancel the reservation itself; it does not cover no-shows or same-day cancellations made after departure.

The part that actually trips people up — booking and paying

You must call to reserve a spot

Southwest does not allow pets to be added to reservations online. To bring your cat, you must call Southwest Reservations at 1-800-I-FLY-SWA (1-800-435-9792), confirm there is a pet spot available on your flight, and register your cat's travel. Your booking is not complete — from Southwest's perspective — until this call has been made.

This is the step most people skip after booking their own tickets online. Showing up at the airport with a cat and no prior phone reservation is a significant risk, because:

The limited spots fill faster than you expect

Southwest limits in-cabin pets to a small number of carriers per flight on a first-come, first-served basis — "space is limited," in Southwest's own words. Third-party sources including Upgraded Points consistently cite six carriers per flight as the standard allocation, though Southwest's own policy page does not publish a specific number. Confirm availability when you call. Across reports from FlyerTalk's Southwest forum and multiple travel communities, pet spots on popular routes during school holidays, Thanksgiving, and summer travel fill up weeks in advance.

On a route from, say, Los Angeles to Denver on a busy travel weekend, those limited spots may be claimed before you decide you need one. The practical rule: call to reserve your cat's spot as soon as you have booked your own ticket, regardless of how far out the trip is.

Some travellers report calling only a few days before a holiday-period flight and being told the pet allocation was already full. On a non-peak Tuesday afternoon, the same situation would be a non-issue. The risk is route- and season-dependent, but the cost of not calling is real.

The fee is paid at the ticket counter — not online, not at the gate

Southwest collects the $125 pet fare at the airport ticket counter when you check in for your flight — not during the online booking process, and not at the boarding gate. Payment must be made by credit card. Southwest does not accept LUV Vouchers, travel credits, or gift cards for the pet fare.

A Southwest Community forum thread flagged a recurring pattern among first-time pet travellers: arriving at the airport expecting to pay online or at the gate, then discovering the counter-only process while under time pressure. Bring a credit card, not a Southwest gift card.

If Southwest flies your route, search Southwest flight availability now — and then call straight away to secure one of the limited pet spots before they fill.

What your carrier needs to meet

Many third-party pet-travel sources cite approximately 18.5 inches long × 9.5 inches high × 13.5 inches wide, but Southwest's current public pet-policy page does not clearly publish a maximum carrier dimension. The right approach: confirm the current size limit directly with Southwest when you call to book, and test your carrier under a 737 seat before your travel day if you can.

What Southwest's policy does confirm:

• The carrier must fit under the seat in front of you
• The carrier must be leakproof and well-ventilated
• Both soft-sided and hard-sided carriers are accepted
• Your cat must be able to stand up, turn around, and move around with ease

If the carrier does not fit under the seat, you will be asked to check it — but Southwest does not accept pets in the hold. A carrier that does not fit means your cat cannot travel on that flight.

For a carrier that works well on US domestic routes and fits within the cited Southwest underfloor dimensions, we recommend the Pecute soft-sided cat carrier. For a full comparison of airline-approved soft-sided carriers with verified dimensions, see our airline-approved cat carrier guide.

At the airport with your cat on Southwest

Check-in: Go to the ticket counter before security. Southwest processes the pet fare here — this is also where staff verify your carrier. Budget an extra 15 minutes over your normal check-in time.

Security: Standard TSA procedure — remove your cat from the carrier, carry your cat through the security scanner while the carrier goes through the X-ray machine. Keep a secure hold on your cat; they cannot be placed on a surface and should go directly from your arms back into the carrier on the other side.

Boarding: Southwest moved from open seating to assigned seating in 2026. Southwest's airport page confirms: “Customers traveling with pet carriers will board with their assigned boarding group.” The old advice to board as early as possible to claim a good seat no longer applies. Your seat is assigned. Confirm in advance — when you call to add your cat — that your assigned seat row has underseat storage on the 737 variant operating your flight. Exit rows and bulkhead rows typically do not.

Inflight: Your cat stays in the carrier under the seat in front of you for the entire flight — during taxiing, takeoff, the flight itself, and landing. Carriers may not be placed on your lap or in the overhead compartment. Pets exhibiting disruptive behaviour (persistent vocalisation, escape attempts, scratching) can be denied boarding at the gate.

Southwest's route restrictions for cat owners

Southwest's pet policy applies to domestic US mainland flights only.

Hawaii: Southwest does not accept in-cabin pets on flights to or from the US mainland to Hawaii. Inter-island travel within Hawaii is permitted, with a lower fee of $35 per carrier. If you are relocating a cat to or from Hawaii, Southwest's mainland routes are not an option — check Delta or United's cargo programmes for Hawaii routes.

International: Southwest does not accept in-cabin pets on any international itinerary.

Puerto Rico: Passengers travelling to Puerto Rico may need to provide an official interstate health certificate from a USDA-approved veterinarian from your home state before entry is allowed. USDA APHIS handles interstate health certificate endorsement (aphis.usda.gov/pet-travel). Confirm the current requirements when you call to reserve.

For context on how Southwest compares to the other major US carriers your route might serve, see our guides to flying Delta Airlines with a cat, flying American Airlines with a cat, and flying United Airlines with a cat.

Frequently asked questions

How much does it cost to fly with a cat on Southwest Airlines?
Southwest charges $125 per carrier, one-way, for domestic US mainland flights, as of May 2026. The fee is paid at the airport ticket counter by credit card. Southwest states that pet fares are subject to change at any time — confirm the current fee when you call to book.

Can I bring two cats on Southwest Airlines?
Yes. Southwest allows up to two cats of the same species in a single carrier, for a single $125 fee. Both cats must fit comfortably inside the carrier and be able to stand and move around. For most adult-cat trips, Delta and American are less favourable for two-cat travel — they generally price by kennel and restrict how many pets can share one carrier. Check each airline's age and same-carrier exceptions before booking.

How do I add my cat to a Southwest Airlines reservation?
Call Southwest Reservations at 1-800-I-FLY-SWA (1-800-435-9792). Pets cannot be added to reservations online. Southwest says space is limited and first-come, first-served — call as soon as you have booked your own ticket.

Is there a weight limit for cats on Southwest Airlines?
Southwest does not publish a combined cat-plus-carrier weight limit. The requirement is that the cat fits comfortably in the carrier, can stand up and move around, and that the carrier fits under the seat. In practice, staff assess comfort at check-in — a visibly cramped cat will be refused.

Can I take my cat as checked baggage on Southwest?
No. Southwest does not accept pets in the hold or as checked baggage. In-cabin carry-on only.

Do cats have to stay in the carrier the whole flight on Southwest?
Yes. Southwest requires pets to remain inside their carrier at all times — in the gate area, during boarding and deplaning, and throughout the flight. Carriers must be stowed under the seat in front of you, not on your lap.

How many pets are allowed on a Southwest flight?
Southwest limits in-cabin pets to a small number of carriers per flight — the airline says space is limited and first-come, first-served. Third-party guides consistently cite six carriers as the standard allocation, though Southwest does not publish a specific number on its policy page. Call early to confirm availability on your specific flight.

Can I fly to Hawaii with my cat on Southwest Airlines?
No — not on mainland-to-Hawaii routes. Pets are permitted on inter-island flights within Hawaii for $35 per carrier. Southwest does not accept in-cabin pets on US mainland to Hawaii flights.

What size carrier does Southwest Airlines accept for cats?
Many third-party pet-travel sources cite approximately 18.5 inches long × 9.5 inches high × 13.5 inches wide, though Southwest does not clearly publish a maximum carrier dimension on its current public pet-policy page. Confirm the current dimensions when you call to book, and test your carrier under a 737 seat before your travel day.

Is the Southwest Airlines pet fee refundable?
Yes — if you cancel your reservation, Southwest refunds the pet fare. No-shows and same-day cancellations made after scheduled departure may not be eligible for a refund.

What to do next

You now know what Southwest allows, how it compares to Delta, United, and American Airlines, and what the two steps are that most people miss: calling to reserve before the limited pet spots fill, and paying at the ticket counter with a credit card on the day.

If Southwest serves your route and your carrier meets the size requirements, search Southwest flights to find available services. If your route is also served by Delta or United, compare the pet policies and your route options in our guides to flying Delta with a cat and flying United with a cat.

For a carrier that fits Southwest's underfloor dimensions and holds up on US domestic routes, see our airline-approved cat carrier guide — or go directly to the Pecute soft-sided cat carrier.

Policy verified from southwest.com and support.southwest.com, May 2026. Airline policies change — confirm directly with Southwest before booking.

Related: For a full fee and policy comparison, see how Southwest compares to other major US airlines.