There is no government or industry certificate called "airline approved". A carrier is approved for your flight if it fits that airline's under-seat limit and your pet fits comfortably inside it. That's it.
Key facts
- There is no official "airline approved" or "TSA approved" certification for pet carriers.
- A carrier of 17 x 10.5 x 8.5 in fits every US airline limit we track.
- Air Canada, Lufthansa and Turkish Airlines accept only soft-sided carriers in the cabin.
- KLM, Lufthansa, Air France and Turkish cap pet plus carrier at 8 kg (17.6 lb).
Listings that say "airline approved" or "TSA approved" are marketing. The TSA doesn't approve carriers at all; it only screens them. Each airline sets its own maximum size, and the numbers differ by up to 3 inches between airlines, and sometimes between aircraft on the same airline.
Under-seat carrier limits by airline
These are the maximum outside dimensions each airline publishes for a pet carrier in the cabin. We read every number off the airline's own policy page.
| Airline | Max carrier size | Other limits |
|---|---|---|
| Air Canada | 43 x 40 x 20 cm (16.9 x 15.8 x 7.9 in) (most jets); 55 x 40 x 27 cm (21.6 x 15.8 x 10.6 in) (Dash 8, E175, CRJ900) | Soft-sided only. |
| Alaska Airlines | 17 x 11 x 9.5 in (soft-sided) | No weight limit |
| Allegiant Air | 18 x 12 x 11 in (soft-sided); 17 x 11 x 10.5 in (hard-sided) | No weight limit |
| American Airlines | 18 x 11 x 11 in (soft-sided); 19 x 13 x 9 in (mainline jets); 16 x 12 x 8 in (American Eagle regional jets) | No weight limit |
| Delta Air Lines | 18 x 11 x 11 in (recommended size) | No weight limit |
| Frontier Airlines | 18 x 14 x 11 in (soft-sided); 18 x 14 x 8 in (hard-sided) | No weight limit |
| Hawaiian Airlines | 17 x 11 x 9.5 in (soft-sided) | No weight limit |
| JetBlue | 17 x 12.5 x 8.5 in (any carrier) | No weight limit |
| Southwest Airlines | 18 x 10.5 x 10 in (any carrier) | No weight limit |
| United Airlines | 18 x 11 x 11 in (soft-sided); 17.5 x 12 x 9 in (hard-sided) | No weight limit |
| WestJet | 41 x 25.4 x 21.5 cm (16.1 x 10 x 8.5 in) (any carrier) | No weight limit |
| Air France | Not published | Max 8 kg with carrier. |
| KLM Royal Dutch Airlines | 46 x 28 x 24 cm (18.1 x 11 x 9.4 in) (any carrier) | Max 8 kg with carrier. |
| Lufthansa | 55 x 40 x 23 cm (21.6 x 15.8 x 9.1 in) (soft-sided) | Soft-sided only. Max 8 kg with carrier. |
| Turkish Airlines | 40 x 30 x 23 cm (15.8 x 11.8 x 9.1 in) (soft-sided) | Soft-sided only. Max 8 kg with carrier. |
Length x width x height, in inches. Metric limits converted from the airline's centimetres. Tap an airline for fees, age rules and sources.
The sizes that fit the most flights
- 17 x 10.5 x 8.5 in fits the published limit of every US airline we track: United, Delta, American, Alaska, Hawaiian, JetBlue, Southwest, Frontier and Allegiant. It's the safest size if you fly more than one airline.
- 18 x 11 x 11 in soft-sided is the size United, Delta and American publish. It gives your pet more room but is too tall for JetBlue, Alaska and Southwest.
- 40 x 28 x 23 cm fits KLM, Lufthansa and Turkish Airlines in Europe, which also cap pet plus carrier at 8 kg (17.6 lb).
- Air Canada is the tightest on most of its jets: 43 x 40 x 20 cm (about 17 x 15.7 x 7.9 in), soft-sided only.
Not sure about yours? Put its measurements into the carrier size checker and it will compare them against every airline at once.
Soft-sided or hard-sided?
Choose soft-sided for the cabin. Soft carriers can flex a little to fit the space under the seat, and some airlines don't accept anything else: Air Canada (since June 2025), Lufthansa and Turkish Airlines all require soft-sided carriers in the cabin. Hard-sided kennels are for pets travelling in the hold.
A soft carrier still has to keep its shape. The pet must be able to stand up and turn around without the sides pressing on it, so a carrier that only fits when squashed won't pass.
How to measure a carrier
- Zip the carrier closed and stand it on the floor.
- Measure the outside, including pockets, handles that stick out and wheels.
- Length is the longest side. Height is the floor to the highest point of the frame.
- Compare height first. The space under a seat is lowest at the back, so height is what usually fails.
Will my pet fit?
US airlines don't set a weight limit for cabin pets; your pet just has to fit. In practice, a pet that can stand, turn around and lie down in a 17 to 18 inch carrier is usually a cat or a small dog. European airlines are stricter: KLM, Lufthansa, Air France and Turkish cap the pet and carrier together at 8 kg.
Measure your pet standing (floor to the top of the head) and lying down (nose to the base of the tail). Both need to fit inside the carrier with a little room to spare.
Getting a carrier through airport security
At a US checkpoint the carrier goes through the X-ray machine empty. You take your pet out and carry it through the metal detector, so a harness and leash make this much easier, especially with cats.
Questions people ask
Is there such a thing as an airline-approved pet carrier?
No. There's no official certification. A carrier is acceptable if it fits the airline's published under-seat size limit, is leak-proof and ventilated, and your pet can stand and turn around inside it.
What does TSA approved pet carrier mean?
Nothing official. The TSA screens pet carriers at the checkpoint but doesn't approve or certify them. Size limits come from the airline, not the TSA.
What size pet carrier fits all airlines?
For US airlines, a carrier no larger than 17 x 10.5 x 8.5 inches fits every published limit we track. In Europe, 40 x 28 x 23 cm fits KLM, Lufthansa and Turkish Airlines.
Can I use a hard-sided carrier in the cabin?
On some airlines, such as United, American, Frontier and Allegiant, which publish separate hard-sided limits. Air Canada, Lufthansa and Turkish Airlines only accept soft-sided carriers in the cabin.
