Flying with a pet from St. Louis introduces a set of logistics that can feel overwhelming — but it doesn’t have to be. St. Louis Lambert International Airport (STL) serves as a central hub for numerous airlines with well-defined pet travel options, and a little insider knowledge goes a long way toward getting your dog or cat from the gate to the destination safely. Whether you’re traveling for a permanent move or a much-needed vacation, the choice of carrier is the single most important decision you’ll make. Airlines vary dramatically in how they accommodate animals, from in-cabin allowances to cargo temperature controls, and St. Louis’s unique position in the heart of the Midwest means you have access to both legacy carriers and pet-focused specialists that prioritize animal welfare.

In this guide, we explore the best airlines for pets departing from St. Louis, break down the fine print on fees and restrictions, and deliver practical advice for booking, preparing, and navigating the airport. The recommendations draw from official airline policies, terminal-specific amenities at STL, and the experiences of frequent pet travelers. By the end, you’ll know exactly which carriers offer the safest and most comfortable experience for your four-legged family member.

Top Airlines for Pets from St. Louis: A Detailed Comparison

Not all airlines treat animals the same way. Some allow only small cats and dogs in the cabin, others have robust cargo programs with climate-controlled compartments, and a select few even fly pets as their sole passengers. We evaluated the major airlines operating out of STL based on safety track records, policy clarity, affordability, and the practicality of their pet travel programs. Here’s how they stack up.

Alaska Airlines: The Gold Standard for In-Cabin and Cargo Pets

Alaska Airlines consistently earns high marks for pet travel, and St. Louis passengers benefit from their multiple daily connections through West Coast hubs like Seattle. Alaska permits small cats, dogs, rabbits, and household birds in the cabin as long as the carrier fits under the seat and the combined weight of pet and carrier does not exceed 20 pounds (including the carrier). The one-way cabin fee is a reasonable $100, and pets must be at least 8 weeks old and fully weaned. What sets Alaska apart is its thoughtful approach to cargo. For larger animals, Alaska offers Alaska Pet Travel, which moves pets in pressurized, temperature-controlled cargo holds. Their promise: pets are never left on the tarmac in extreme heat or cold, and staff receive routine training on animal handling. Booker can reserve a spot for a pet up to 24 hours before departure, and the airline’s dedicated pet policy page lists all embargoes and breed restrictions clearly. For St. Louis flyers heading to Alaska, Hawaii, or the Pacific Northwest, this is often the safest bet.

Frontier Airlines: Affordable and Pet-Friendly with Limited Routes

Frontier’s low-cost model still makes room for pets, and their direct flights out of St. Louis to leisure destinations are a big draw. Frontier allows cats, dogs, rabbits, guinea pigs, hamsters, and small household birds in the cabin only — no cargo or checked pets. The fee is $99 each way, and the carrier must be soft-sided and fit in the foot space. Pets must be at least 8 weeks old. Frontier caps the number of pets per flight, so early booking is critical. While the budget-friendly fare structure may appeal to penny-conscious travelers, be aware that Frontier’s network from St. Louis is more seasonal and limited to certain cities like Denver, Orlando, and Las Vegas. If your route aligns, it’s a viable option. Check the most recent Frontier pet policy before you book, as rules around same-day changes and cancelations differ.

American Airlines: Reliable and Widely Available from STL

With one of the largest presences at Lambert Airport, American Airlines offers extensive domestic and international connectivity. For cabin travel, the rules are standard: small cats and dogs in a carrier that fits under the seat, maximum 20 pounds combined weight. The fee is $125 each way. American’s Animal Stow program handles larger pets as checked baggage on select flights, but availability depends on aircraft type and outside temperature limits. Unlike some competitors, American doesn’t book pets into a separate cargo stream; they travel with the checked luggage but in a pressurized compartment. International and certain domestic routes may require cargo via American Airlines Cargo, which has its own set of rules. A standout recommendation: call American’s pet desk directly at least 48 hours before the flight to confirm availability of Animal Stow, since online booking doesn’t always reflect real-time capacity. That number, 1-800-433-7300, can save you a world of hassle. For the latest, visit American’s pet travel page.

Delta Air Lines: Solid Cargo Program but Limited In-Cabin Flexibility

Delta offers in-cabin pet travel on domestic flights for $125 each way, with the same size and weight limits as other mainline carriers. The real strength for larger animals is Delta Cargo, which operates a temperature-controlled live animal service. However, that service is not available on all routes, and from St. Louis, connections through Atlanta or Minneapolis can make the journey longer. Delta also imposes breed restrictions for snub-nosed dogs and cats in the cargo hold due to respiratory concerns. In-cabin, pets must remain inside their carrier during the entire flight, and the carrier must be leak-proof and ventilated. Because Delta’s cargo program requires a separate booking process and advance health documentation, give yourself a minimum of two weeks to arrange everything. Their pet travel overview is one of the clearest in the industry.

Southwest Airlines: Budget-Friendly Cabin-Only Option

Southwest boasts the lowest in-cabin pet fee among major U.S. carriers at just $75 per flight segment. The catch? Southwest only permits small, vaccinated cats and dogs — no other species — and does not transport pets as checked baggage or cargo. All pets must ride in an approved carrier under the seat in front of you, and you can’t occupy an exit row or a bulkhead seat. This makes Southwest ideal for short-haul St. Louis flights (e.g., to Chicago Midway or Dallas Love Field) as long as your animal is under 20 pounds. There’s a limit of six pet carriers per flight, so book early and call to add your pet to the reservation right after you purchase your ticket. The straightforward policy and friendly crew often make this a stress-free experience for small dogs and cats.

United Airlines: PetSafe Cargo for Larger Breeds

United’s in-cabin fee is $125, matching industry averages, but their standout feature is PetSafe, a dedicated program for animals traveling in the cargo hold. PetSafe includes temperature-controlled vehicles, specialized holding areas, and trained personnel. However, United has faced scrutiny in the past regarding pet incidents, prompting them to overhaul safety protocols. They now enforce strict breed and temperature embargoes. For flights from St. Louis, check if your specific route and aircraft accept PetSafe bookings. United’s website allows you to search by flight number to confirm pet eligibility. For peace of mind, many St. Louis veterinarians recommend paying close attention to crate requirements — United’s crate specifications are among the most rigorous, and failing to meet them can result in denied boarding.

Pet Airways: A Pet-Only Alternative Worth Watching

Pet Airways has generated interest among St. Louis pet owners because of its unique model: all-pet flights without human passengers. Animals travel in the main cabin in secured crates with staff monitoring them throughout the flight. Service from St. Louis is relatively new and may not operate daily, so availability depends on seasonal schedules. The appeal is obvious — no cargo hold, temperature extremes, or baggage handling conveyors. However, ticket prices tend to be higher, and the limited route network may require coordinating with a human airline for your own travel. For those willing to explore this solution, checking current routes and availability directly on the Pet Airways website is a must. It’s especially worth considering for long-distance relocations when driving isn’t practical.

In-Cabin vs. Cargo: Making the Right Choice for Your Pet

One of the first decisions you’ll face is whether to bring your pet into the airplane cabin or send them as cargo/checked baggage. The answer typically depends on size, but also on your pet’s temperament, health, and even breed.

The In-Cabin Experience

In-cabin travel is undeniably less stressful for most animals because they remain close to you. The ambient noise, cabin pressure, and temperature are the same as for human passengers. However, carriers must fit entirely under the seat, limiting this option to small dogs and cats typically under 20 pounds. Soft-sided carriers are recommended since they compress more easily into tight footwells. Pets must remain inside the carrier for the entire flight, and any vocalizing or aggressive behavior can result in being asked to rebook on a later flight. Airlines also restrict the number of in-cabin pets — often four to six per flight — so reserve early.

Cargo and Checked Pet Travel: Safety First

For medium to large dogs, cargo is often the only choice. The biggest concern here is temperature and ventilation. Leading airlines now use climate-controlled cargo bins, especially those with active temperature monitoring, and they will refuse transport if external temperatures exceed safe limits (typically below 45°F or above 85°F for certain breeds). Crate quality is paramount: hard-sided crates with metal hardware, secure door latches, and absorbent bedding are mandatory. Label the kennel with “Live Animal” stickers and attach a water bottle that can be filled from outside. Avoid feeding your dog right before the flight to reduce the risk of bloat or vomiting. When booking cargo, always ask whether the aircraft is equipped with active climate control in the lower deck — this is not a given on all planes, especially regional jets.

Breed Restrictions and Snub-Nosed Considerations

Many airlines ban brachycephalic (short-nosed) breeds from cargo travel due to their compromised respiratory systems. Bulldogs, pugs, Boston terriers, Persian cats, and similar breeds should only fly in the cabin if space and weight allow. American, Delta, United, and Alaska all publish up-to-date breed restriction lists. If you own a snub-nosed breed and travel is unavoidable, a pet-only airline like Pet Airways may be a safer route, or you might need to arrange ground transportation instead.

Booking and Preparing for a Smooth Flight from St. Louis

A successful trip begins days or even weeks before you leave home. From securing your pet’s spot on the manifest to assembling a travel kit, preparation can eliminate the most common pain points.

How to Book Your Pet’s Ticket

When booking your own seat, never assume your pet can simply be added at check-in. Most airlines require you to notify them immediately — either online through “Add a Pet” options or by calling reservations. After booking, you’ll receive a confirmation for the animal, but that doesn’t guarantee your pet will board if you don’t meet check-in requirements. For in-cabin travel, arrive at the airport at least 2 hours before domestic flights and 3 hours for international. For cargo or checked pets, the cutoff is often 90 minutes to 2 hours prior to departure. Have your pet’s reservation number handy, and confirm with the gate agent upon arrival that your pet is on the final manifest.

Health and Documentation Essentials

While a health certificate is not always required for domestic travel, it’s a smart precaution — and some airlines still request one. The certificate, issued by a USDA-accredited veterinarian, must be dated within 10 days of your flight. It confirms your pet is free of infectious disease and fit to fly. For international journeys, requirements escalate: you’ll need an international health certificate endorsed by the USDA, proof of rabies vaccination, and possibly a microchip and other country-specific entries. Check the destination country’s import requirements via the USDA APHIS Pet Travel website. Keep both digital copies and printed versions of all documents, and consider a quick vet visit to discuss anxiety management — but never sedate your pet without veterinary guidance, as altitude can amplify drug effects.

Choosing and Packing the Right Carrier

Airline-approved carriers aren’t just a suggestion; they’re rigidly enforced. For in-cabin, look for a soft-sided carrier with mesh panels and a leak-proof bottom. Maximum dimensions vary by airline but are generally around 18.5” x 8.5” x 13.5”. For cargo, a hard-sided crate made of rigid plastic with secure metal bolts is required. It must be large enough for your pet to stand, turn around, and lie down naturally. Attach a small bag of dry food to the top of the crate in case of delays and include a frozen water bowl or clip-on bottle. Line the bottom with a vet-recommended pee pad under a soft blanket. Check the carrier’s latches with zip ties — not to lock, but to prevent accidental opening — and write your contact information in large permanent marker on the outside.

STL has made strides in becoming more pet-friendly, though it’s still a busy airport. Knowing where to go and what to expect can keep your pet calm during the pre-flight phase.

Pet Relief Areas at STL

Both terminals have designated pet relief areas. Terminal 1 (main terminal, serving most major airlines) features an indoor relief station post-security near Gate A14, complete with artificial turf, a fire hydrant, and waste bags. Terminal 2 (Southwest, Frontier) has an outdoor relief area that requires going back through security, which is less convenient. If you’re flying out of Terminal 2, plan to give your pet a thorough break before passing through the checkpoint. Some passengers use the grassy strips outside the terminal arrival areas for a final potty stop — just clean up thoroughly afterward.

Security Screening with a Pet

At the TSA checkpoint, you’ll need to remove your pet from the carrier while the carrier goes through the X-ray machine. Carry your pet in your arms or on a leash (without a collar, if possible) through the metal detector. If your pet is small and docile, this is quick. For anxious animals, request a private screening room where you can be seated with your pet while the carrier is inspected. Notify the TSA officer ahead of time. Remember that leashes with metal parts can set off the alarm; a simple slip lead is ideal. Practice carrying your pet calmly at home well in advance.

At the Gate and Boarding

Find a quiet corner near your gate, away from loud announcements and foot traffic. Place the carrier against the wall or under your seat in the waiting area to create a sense of security. Some pets appreciate a lightweight cover draped over the carrier (leaving ventilation gaps) to reduce visual stimuli. Boarding procedures vary: some airlines allow pet passengers to pre-board, others treat them like regular boarding groups. Gate agents are usually receptive if you explain that you’d like extra time to settle. Once on board, slide the carrier under the seat and avoid opening it until you’ve landed — no matter how plaintive the whines may become.

Tips for a Stress-Free Journey for Both of You

Even the most prepared travelers hit bumps. These strategies, gathered from veterinary experts and frequent pet passengers, can turn a potentially nerve-wracking day into a manageable one.

  • Acclimate early: Let your pet explore the carrier for short periods at home with a favorite toy or blanket. Gradually increase the duration, and take a few car rides inside the carrier to associate it with neutral or positive experiences.
  • Skip the full meal: Feed a light breakfast at least 4 hours before the flight. A small amount of water is okay, but avoid filling the dish to prevent motion sickness.
  • Check the weather: Extreme temperatures can lead airlines to refuse cargo pets. Even if your destination is mild, a layover city with a heatwave might cause a last-minute denial. Have a backup plan for that scenario.
  • Bring the right leash and harness: A secure, escape-proof harness is better than a collar for navigating the airport. Attach an ID tag with your cell number and a backup contact.
  • Stay calm yourself: Pets pick up on owner anxiety. Speak in a low, soothing tone, and avoid making a big production out of goodbyes at the cargo drop-off.
  • Have an emergency kit: Include a collapsible bowl, bottled water, a small bag of your pet’s regular food, a basic first-aid kit, and copies of all documentation in a zip-top bag.

By combining the right airline selection with thorough preparation, you can transform pet air travel from a source of dread into a simple logistical step. St. Louis travelers are fortunate to have access to carriers with strong safety records and flexible options for different animal needs. Whether you choose Alaska for its dedicated pet focus, Southwest for its budget-friendly cabin policy, or even Pet Airways for the ultimate species-centric experience, the key is planning ahead and staying informed. Safe travels to you and your companion on your next journey out of the Gateway City.