Best Soft-Sided Pet Carriers for Flying With a Cat or Small Dog

An under-seat pet carrier has to pass two inspections, and the packaging only talks about one of them. The first is the size check at the gate, where the bag has to fit entirely under the seat in front of you. The second is the welfare check, where the animal inside has to have room to stand, sit up, lie naturally and turn around. A carrier that passes the first by squeezing the animal fails the second, and either failure can end the trip at the gate.

Both checks are written down. IATA's operational guidelines for in-cabin pet transport, first published on 15 July 2026, tell check-in staff that the container must let the pet stand, sit erect, lie in a natural position and turn about normally while standing. Gate agents are told to confirm that soft and rigid cabin containers are secure, well ventilated, appropriately sized and capable of fitting entirely under the seat in front. If a container is non-compliant or the pet appears distressed, boarding must be denied.

The size box itself belongs to the airline. Alaska Airlines' own guidance for dogs in the cabin, published on 26 August 2026, sets it at a soft-sided carrier no larger than 17 x 11 x 9.5 inches, at $100 per carrier each way. Other airlines print other numbers, and some vary them by aircraft.

Here is the problem the three picks below have to solve. Not one of them is 9.5 inches tall at rest. That is normal for this category, and it is why soft sides exist at all: the carrier gives a few inches under the seat and springs back in the terminal. So the question for each one is how it gives, how much room is left when it does, and what else it can do once you land.

Prices are Amazon's on 19 October 2026, with the size beside each.

What decides the purchase

The airline's printed dimensions, before anything on the box. Look up the exact numbers for the airline and, where it publishes them, the aircraft. The phrase "airline approved" on a pet carrier is not a certification issued by anyone, a point covered in full in what an airline approved pet carrier actually means. Then measure the carrier against that box.

How the height comes down. A carrier that is 10.5 or 11 inches tall has to lose an inch or more to meet a 9.5-inch limit. Some do it with a frame designed to be pressed down at one end. Others rely on soft panels that simply compress. The first is predictable. The second depends on how full the bag is and how the animal is lying.

Room inside, measured on the animal. Measure your pet from nose to base of tail and from floor to the top of the head. The IATA welfare test is about posture, so a 10 lb cat that is long in the body can fail a carrier rated to 15 lb.

Top entry. Lowering a cat into an open top is far easier than pushing it through a front door, and the same goes for a small dog that braces its legs. Training a cat to the carrier weeks before the flight matters more than any feature, and a top opening makes that training easier.

What it does after landing. A trip by air usually includes a drive at each end. Most soft carriers are cargo in a car. One here is independently certified as a car restraint, and that is worth knowing before deciding how much to spend.

The picks

How they compare

Carrier	Size (in)	Pet limit	How it fits under a seat	Car restraint	Price
Sherpa Original Deluxe, Medium	17 x 11 x 10.5	16 lb	Spring frame, rear presses down	Not certified	$72.59
Sleepypod Atom	17 x 8.5 x 10.5	12 lb	Narrow footprint	CPS certified, 5 Star	$139.99
Henkelion Collapsible	17 x 11 x 11	15 lb	Soft panels compress	Not certified	$19.02

Who each one is wrong for

The Atom is wrong for a cat over 12 lb, and that limit is firm because it is the weight the certificate was issued at. A heavier cat can still fit physically, but the crash rating stops applying, and the rating is the reason to pay for it.

A long-bodied cat or a dachshund-shaped small dog can be a poor match for the Sherpa Medium even under 16 lb. An animal that cannot turn around inside fails the IATA welfare check whatever it weighs, so measure the pet against the interior.

Frequent flyers should skip the Henkelion. It is a fair carrier for one trip or an occasional one. A bag that goes through gate checks every month benefits from a frame that controls how it compresses, which is what the Sherpa adds.

All three are wrong for a pet that has never spent time in a carrier. The gate is the worst possible place to discover that a cat will not go in, and an animal that arrives at check-in in obvious distress can be refused boarding under the IATA guidance.

And all three are the wrong answer for a pet too large for the cabin. A dog that does not fit under a seat travels as checked baggage or cargo, in a rigid kennel built to a different standard, which is the territory of the best dog crates rather than this list.

Before the flight

Check the airline's dimensions against the carrier with a tape measure at home, pressing the carrier down the way it will be pressed under a seat, with the animal inside. A bag that only meets the limit when empty does not meet it.

Book the pet when you book the seat. Alaska's guidance says to buy the passenger ticket first and then call to reserve pet space, because space is limited. Cabin pet space runs out, so a pet added late can find the flight full.

Start practising with the carrier weeks ahead. Leave it open in a room the household uses, put the pet's bedding in it and feed treats or meals inside it. A pet that treats the carrier as a bed gets through a gate check calmly. The Sleepypod's plush base is built for exactly that, and the Sherpa's liner does the same job.

Plan the drive. An uncertified carrier is simply cargo in a car. The crash-test evidence on pet restraints in cars explains why a carrier loose on a seat is a poor idea, and the guide to certified cat carriers covers what a CPS certificate does and does not promise.

Questions people actually ask

What size pet carrier fits under an airline seat?

It depends on the airline and sometimes on the aircraft. Alaska Airlines publishes a soft-sided limit of 17 x 11 x 9.5 inches for dogs in the cabin. Check your airline's own published dimensions before buying, and measure the carrier compressed, with the pet inside.

Are soft-sided or hard-sided carriers better for flying in the cabin?

Soft-sided, for most people. A soft carrier can give an inch or two to fit under a seat, which a rigid one cannot. IATA's in-cabin guidance covers both kinds, so the deciding factor is the airline's size box.

How much room does my pet need inside the carrier?

Enough to stand, sit up, lie in a natural position and turn around while standing. That is the standard IATA's in-cabin guidelines tell check-in staff to apply. Measure your pet nose to tail and floor to head and compare it with the carrier's interior, not just its weight rating.

Can I use the same carrier in the car?

You can carry the pet in it, but most soft carriers offer no crash protection. Of the three here, only the Sleepypod Atom holds a Center for Pet Safety certificate, at 12 lb. The other two are cargo in a car.

Is an airline approved pet carrier guaranteed to be accepted?

No. No agency issues an airline approved certification. The airline's published dimensions and the gate agent's check decide it. Sherpa places this carrier in its own Guaranteed On Board programme, which is a brand promise rather than an airline rule.

Sources

• IATA Operational Guidelines for In-Cabin Pet Transport, Edition 1, 15 July 2026
• Alaska Airlines: what to know before traveling with a canine companion, 26 August 2026
• Center for Pet Safety: Sleepypod Atom certification
• Sleepypod Atom, manufacturer page
• Healthy Spot: Sleepypod Atom specifications
• Sherpa Original Deluxe Travel Bag Pet Carrier, manufacturer page