Flying with a pet from Fort Collins, Colorado takes more than just buying a ticket. Picking an airline that treats animal passengers with care—and that has policies that match your pet’s size, breed, and temperament—can turn a nerve-wracking experience into a predictable routine. The best carriers for pet owners departing from this region offer clear in-cabin guidelines, transparent fees, and ground staff who know how to handle animals. Alaska Airlines and Frontier Airlines stand out for letting cats and small dogs ride in the cabin under your seat, but there are half a dozen other carriers serving Denver International Airport that draw pet owners from Fort Collins every day.

What Matters Most When Choosing a Pet-Friendly Airline

Beyond the basic yes-or-no on animals, several factors separate a decent pet policy from one that works in real life. You’ll want to look at cabin weight limits, carrier dimensions, per-flight pet quotas, and whether the airline accepts your pet’s breed at all. Fees also stack up fast, especially on round trips. A few minutes of research before you book can keep you from discovering—at the check-in counter—that your carrier is half an inch too tall or that your dog’s snub nose is on a no-fly list.

  • Cabin fees typically run between $95 and $150 each way per pet, nonrefundable.
  • Most airlines cap the combined weight of pet and carrier at 15 to 20 pounds for cabin travel.
  • Only a set number of pets are allowed in the cabin on any given flight—often four to six, depending on aircraft type.
  • Checking your pet as cargo or baggage is only available on certain routes and during weather-safe months.
  • Health certificates and specific carrier requirements are universal, but deadlines and form details vary by airline and destination.

Top Airlines for Pet Travel from Fort Collins

Although Fort Collins has its own regional airport (Fort Collins-Loveland Municipal, FNL), most commercial flights with realistic pet options operate out of Denver International Airport (DEN), roughly 65 miles south. That extra drive opens up a far wider selection of airlines, many with well-established pet programs. Here’s how the leading carriers compare.

Major Carriers with Thorough Pet-Friendly Services

Delta Air Lines allows pets to travel in the cabin, as checked baggage, and through its dedicated Delta Cargo service. For in-cabin travel, the pet must fit in a soft-sided or hard-sided carrier that stows under the seat in front of you. Delta’s cabin pet fee is $95 each way for flights within the U.S., Canada, and Puerto Rico. When you use the checked baggage option, pets travel in a pressurized, temperature-controlled cargo hold on the same flight as you. Delta Cargo is available for animals that exceed cabin limits and for species like birds and small rodents, though the booking process is separate and more complex. Weather embargoes apply: if the temperature at any point in the journey is forecast above 85°F or below 20°F, Delta may refuse to accept checked pets. The airline also restricts snub-nosed breeds—including Bulldogs, Pugs, and Boston Terriers—from traveling as checked baggage year-round. Delta’s pet travel page keeps breed lists and embargo dates updated seasonally.

Alaska Airlines regularly earns praise from pet owners for its straightforward in-cabin policy. Dogs, cats, rabbits, and household birds can ride in the main cabin for a $100 fee each way. Pets must remain inside an approved carrier—maximum dimensions 17" x 11" x 9.5" for hard-sided or 17" x 11" x 9.5" for soft-sided—and the carrier counts as your one carry-on item. Alaska does not transport pets as checked baggage, so larger dogs and cats that won’t fit under the seat must go through the airline’s cargo program, Alaska Air Cargo, which requires a separate reservation. The airline limits the total number of pet carriers in the cabin to five per flight, and only one carrier per passenger is allowed. Alaska also has a short list of brachycephalic breeds that can only fly in the cabin, never cargo. Full details and pet carrier specifications are on Alaska’s pet policy page.

United Airlines offers both in-cabin travel and a comprehensive cargo program called PetSafe. In-cabin fees are $150 each way, plus a $125 fee for each additional stopover of more than four hours. The in-cabin carrier size limit is 18" x 11" x 11" for hard-sided and 18" x 11" x 11" for soft-sided, and the pet must remain completely inside. United permits up to two pets per passenger in the cabin, but they must be the same species and fit in a single carrier; otherwise, an extra seat purchase might be needed. For cargo, PetSafe handles larger animals and even some species not allowed in the cabin, but the service is only available at certain airports and during specific times of year. United publishes a detailed list of restricted breeds—dogs with short snouts, muscular builds, or aggressive reputations—and will not accept them as cargo. The airline also requires a health certificate issued within 10 days of travel, and for international trips, the timeline shrinks to just a few days. The United pets page walks you through every scenario.

American Airlines permits cats and dogs in the cabin if the carrier fits under the seat, with a $125 fee per kennel each way. American also allows checked pets for active-duty U.S. military and State Department personnel on official orders, but otherwise suspended its checked pet program for non-military customers on most routes. Cargo service is available through American Airlines Cargo for animals that don’t qualify for cabin travel, though the process is separate from passenger ticketing. As with other major carriers, brachycephalic breeds cannot fly as cargo, and cabin pets are limited to a few carriers per flight.

Regional and Budget Airlines for Pet Owners

If cost is a primary concern, low-cost carriers that fly from Denver can still get your pet where you’re going—often for a lower base fee, but with tighter restrictions. Frontier Airlines charges $99 per pet, one way, and only allows cats and dogs in the cabin. The pet must be in a carrier that fits under the seat, with maximum dimensions of 18" x 14" x 8". Frontier does not transport pets as checked baggage or cargo, so larger animals cannot fly. The airline also specifies that pets cannot be seated in row one or in the exit row, and only one pet per passenger is permitted. Frontier’s pet travel page outlines all restrictions.

Southwest Airlines welcomes small vaccinated domestic cats and dogs in the cabin for a $95 fee each way on domestic flights. The carrier must fit under the seat—soft-sided is strongly preferred—and Southwest’s size limit is 18.5" x 13.5" x 9.5". Pets count as a carry-on item, and each customer may bring only one pet carrier. Southwest does not accept pets in the cargo hold, so large dogs and exotic animals are out of luck. The airline also limits the number of pet carriers to six per flight, and booking early is the surest way to secure a spot. Southwest’s size restrictions and fee structure are clearly spelled out on its website, making it a consistent favorite for budget-minded travelers with small pets.

Some regional airlines operating from smaller airports in northern Colorado may offer limited pet services, but these often come with day-of restrictions and less flexibility on carrier sizes. Before you book a flight out of Fort Collins–Loveland Airport, confirm directly with the airline that its pet policy matches your needs, as many small carriers do not have the same temperature-controlled cargo facilities as the big jets out of Denver.

Choosing Between Fort Collins-Loveland and Denver International

The Fort Collins–Loveland Municipal Airport (FNL) is convenient for locals, but its commercial flight schedule is sparse and primarily served by a handful of carriers that may not accept pets or may impose stricter limits. Denver International Airport, by contrast, is one of the country’s busiest hubs. It offers full-service pet relief areas inside the terminals—including a post-security outdoor area in Concourse A and indoor relief stations in Concourses B and C—plus staff trained in handling animals. DIA’s pet relief area map makes locating these spots easy before your flight. The wider choice of airlines at DEN also means you can often find more flexible options for large dogs or multi-pet households. For most Fort Collins pet owners, the drive down I-25 is worth the expanded set of policies, better cargo options, and dedicated animal facilities.

Understanding Airline Pet Policies Inside and Out

Even among airlines that allow pets in the cabin, the fine print can catch you off guard. Here’s how the main policy categories work and what you need to look for when comparing carriers.

In-Cabin Pet Policies

In-cabin travel is the least stressful option for most small animals and their owners. Airlines generally allow cats and small dogs, and some also accept rabbits, guinea pigs, and household birds. The pet must stay inside an approved carrier that slides under the seat in front of you. Carriers must be leak-proof and well ventilated; most airlines publish precise maximum dimensions, often around 17–19 inches long, 11–14 inches wide, and 8–11 inches tall. Soft-sided carriers offer a bit more interior room and are easier to squish into tight spaces, but hard-sided kennels are also accepted. The combined weight of pet and carrier usually must not exceed 15 to 20 pounds, and the animal must be able to stand up and turn around without touching the top.

Pets must be at least 8 weeks old for domestic flights, and airlines may require a minimum age of 10 weeks or older for connections or international itineraries. On many airlines, you cannot sit in an exit row or a bulkhead seat when traveling with a pet, and the carrier must remain under the seat for the entire flight—no taking the animal out during taxi, takeoff, or landing. Some carriers, such as Delta and United, limit the total number of in-cabin pets to six or fewer per flight, making early booking essential.

Checked Baggage and Cargo Pet Travel

When an animal is too large to fit under a seat, checked baggage or cargo service becomes the only option—and it comes with a different set of rules. Checked pets travel in pressurized, climate-controlled cargo compartments on the same aircraft as the passenger. The crates must be hard-sided, ventilated on at least three sides, and securely fastened with metal hardware (no plastic fasteners). Airlines strictly enforce crate sizing: the animal must have enough room to stand, turn, and lie down naturally without touching the crate walls or top. Attaching a water dish and a food dish to the interior door is often mandatory, and you will need to affix a live animal sticker and directional arrows to the crate.

Weather restrictions are the biggest wildcard. When the temperature at any point on the route exceeds 85°F or falls below 20°F (or 45°F for some short-nosed breeds), airlines may embargo all animal checked baggage. That means a hot summer afternoon or a frigid winter morning can cancel your pet’s ticket even if yours is confirmed. For this reason, booking a direct morning or evening flight in moderate seasons improves your odds. Cargo services like United PetSafe and Delta Cargo operate year-round but require separate reservations and often higher fees, plus drop-off and pick-up at airport cargo facilities, which are located away from passenger terminals.

Breed and Size Restrictions

Every airline that transports animals maintains a list of breeds it will not accept as cargo because of health risks, and many extend these restrictions to in-cabin travel during certain weather conditions. The core concern is brachycephalic (flat-faced) animals—dogs like English Bulldogs, French Bulldogs, Pugs, Boston Terriers, Boxers, and Shih Tzus, as well as cat breeds such as Persian and Himalayan. These animals are more prone to respiratory distress and overheating, especially in cargo holds. Alaska, Delta, United, American, and others publish breed-specific lists that are updated regularly. If your pet’s breed appears on a restricted list, your only option is usually in-cabin travel, provided the pet fits the size and weight limits. Some airlines go further and ban any animal with a snub nose entirely, regardless of travel method.

Size matters in the cabin, too. Even if your dog is a non-restricted breed, he won’t fly in the cabin if he can’t fit inside the carrier dimensions. Carriers that bulge, poke out into the aisle, or fail to slide entirely under the seat will be rejected at the gate. If your dog weighs 25 pounds but is short and blocky, he might still exceed the height or length constraints of an under-seat kennel—measure carefully. The carrier’s dimensions must match the airline’s specific guidelines, and you’ll want to note that soft-sided and hard-sided numbers often differ even for the same airline.

Costs, Booking, and Preparation Tips

Knowing the numbers and having your paperwork in order before you leave home removes most of the in-airport scramble. Here’s a breakdown of what to budget for and how to prepare.

Price Comparison and Fees for Pet Travel

Pet travel fees are almost always nonrefundable and are charged each way. A round trip with a single pet will cost between $190 and $300 on top of your own ticket, depending on the airline. Frontier offers one of the lowest fees at $99 per direction, while United’s $150 fee is at the higher end. Southwest competes at $95. Alaska Airlines sits squarely in the middle at $100. The fee structure can also vary by itinerary: United charges an additional $125 for each layover longer than four hours, and American tacks on extra for transatlantic or transpacific flights. These fees are per carrier, so if you’re traveling with two small cats in one approved kennel, you’ll often pay a single fee—check that the airline allows multiple pets in one carrier, as not all do. Cargo fees are a different calculation entirely and are based on crate dimensions and weight, not a flat rate; shipping a large dog in cargo domestically can easily exceed $400 one way.

Advanced Booking Strategies

Because airlines cap the number of pets allowed in the cabin, booking early is the single most effective way to avoid disappointment. Most carriers will let you add a pet during the online booking process, often through a “Special Services” or “Traveling with a pet” option on the passenger details page. After selecting the flight and confirming your own reservation, make sure you get a confirmation email that explicitly mentions your pet. If you don’t see the pet listed on the itinerary, call the reservations desk immediately. Airlines commonly require that you contact them directly if your pet belongs to a restricted breed, even for in-cabin travel, to get an additional pre-approval code.

If you plan to use cargo or checked baggage service, book the animal’s spot at the same time you buy your own ticket—cargo space is limited and often sells out during holiday rush periods. Some airlines require a mandatory waiting period between cargo booking and travel, so last-minute arrangements can be impossible. Also keep in mind that if you’re flying a multi-leg itinerary, each flight segment must individually confirm pet space; it’s possible to have your pet accepted on the first leg but waitlisted on the connection. A direct flight removes that risk.

Essential Documentation and Preparation

No matter which airline you choose, you’ll need a health certificate issued within 10 days of your outbound flight from a licensed veterinarian. The certificate, sometimes called a Certificate of Veterinary Inspection, must state that the animal is free from infectious disease and fit to fly. Some states and international destinations mandate additional endorsements from the USDA or proof of specific vaccinations, such as rabies. For travel outside the contiguous U.S., including Hawaii, the requirements become much more complex and can require blood tests and months of advance work.

Pack a travel-ready kit: an airline-compliant carrier with absorbent bedding, a collapsible water dish, food if the trip is long, leash, collar with ID tag, and any regular medications. Get your pet accustomed to the carrier for several weeks before departure by leaving it open at home with treats and familiar toys inside. On the day of travel, avoid feeding a large meal right before heading to the airport—a light meal three to four hours in advance reduces the chance of an upset stomach in the air. Plan potty breaks strategically. Denver International Airport has dedicated relief areas where dogs can stretch their legs before going through security, and post-security areas are available in concourses A, B, and C. While pet relief areas inside the terminals are designed with artificial turf and waste stations, it’s smart to bring your own waste bags and a small towel just in case.

Final Tips for a Safe and Predictable Flight

Pulling everything together, a successful pet journey from Fort Collins boils down to three things: pick the airline whose policies and fees align with your pet’s size and health, book early and confirm in writing, and prepare your animal and paperwork days—not hours—ahead. When you compare the major players, Alaska Airlines and Frontier consistently offer the most pet-owner-friendly in-cabin experience, with Delta and United stepping in for those who need cargo capacity or have more complex itineraries. Budget-conscious travelers will find Southwest a steady option, even if it means a drive to Denver.

Always check the airline’s current pet page within 24 hours of departure; policies, embargoes, and fees can change, and a winter storm or heat wave may trigger last-minute restrictions. If your pet is larger, a restricted breed, or simply too nervous for a noisy cabin, talk to your veterinarian about whether cargo travel or alternative transport is safer. Ultimately, the right airline will be the one that gives you peace of mind from Fort Collins to your final destination—keeping your pet secure, comfortable, and close at hand.