Short answer: In-cabin pet carrier limits vary by airline from 8 inches to 11 inches in height (20–28 cm), so there is no single “airline-approved” size that fits every carrier. The table below shows the official 2026 limits for 12 major airlines, checked against airline websites in September 2026 — always confirm with your airline before you book.
Airline-Approved Pet Carrier Sizes 2026: The Chart
All sizes below are maximum carrier dimensions (length × width × height). Soft-sided carriers are recommended by every airline in this list because they compress to fit under different seats. Dimensions verified against official airline pages, September 2026.
| Airline | Soft-sided carrier max | Hard-sided carrier max | Weight limit |
|---|---|---|---|
| United | 18″ long (45.7 cm); height varies by aircraft (737 MAX 9: max 10″) | 17.5″ x 12″ x 7.5″ (44.5 x 30.5 x 19 cm) | Pet fits comfortably in carrier |
| Frontier | 18″ x 14″ x 11″ | 18″ x 14″ x 8″ | No stated max |
| Allegiant | 18″ x 14″ x 8″ (46 x 36 x 20 cm) | 18″ x 14″ x 8″ | Pet + carrier ≤ 25 lb |
| KLM | 46 x 28 x 24 cm (18″ x 11″ x 9″) | Not permitted in cabin | Pet + carrier ≤ 8 kg |
| Alaska | 17″ x 11″ x 9.5″ | 17″ x 11″ x 7.5″ (not listed for cabin) | No stated max |
| ITA Airways | 55 x 40 x 23 cm (21.7″ x 15.7″ x 9.1″), total ≤ 118 cm | Same limit | 12 kg domestic / 8 kg other |
| Finnair | 55 x 40 x 23 cm (Finnair) / 55 x 40 x 20 cm (Norra) | 35 x 30 x 20 cm | Pet + carrier ≤ 8 kg |
| Turkish Airlines | 40 x 30 x 23 cm (15.7″ x 11.8″ x 9.1″) — soft only | Not permitted (soft bag only) | Pet + carrier ≤ 8 kg |
| JetBlue | 17″ x 12.5″ x 8.5″ (43.2 x 31.8 x 21.6 cm) | Same limit | Pet + carrier ≤ 20 lb |
| American | 18″ x 11″ x 11″ (46 x 28 x 28 cm), all flights | 19″ x 13″ x 9″ mainline / 16″ x 12″ x 8″ Eagle | Pet + carrier ≤ 20 lb |
| Delta | Recommended 18″ x 11″ x 11″ (45 x 28 x 28 cm), varies by aircraft | Same recommendation | Carrier must fit under seat |
| Southwest | 18.5″ x 13.5″ x 9.5″ (47 x 34 x 24 cm) | Same limit | Carrier must fit under seat |
Policies change frequently and under-seat space varies by aircraft type. Confirm the current limit on your airline’s official website before travelling.
Why Do Airline Carrier Limits Vary So Much?
Every airline measures the under-seat space of its own fleet, and those spaces differ by aircraft and seat row. That is why Allegiant and Frontier enforce an 8-inch height for hard-sided carriers while American and Delta accept 11-inch soft carriers. Travelers regularly report that Allegiant firmly tolerates only 8 inches high, 14 wide and 18 long — the 8-inch height rules out many standard carriers, including most that fit a cat comfortably standing up.
How Do I Choose the Right Size for My Flight?
Work backwards from your ticket, not from the carrier:
- Check the airline and aircraft type for every segment — regional jets (American Eagle, United Express) often have tighter limits than mainline aircraft.
- Measure the carrier’s maximum external dimensions, not the interior, with a rigid tape along the widest points.
- If you fly multiple airlines, size to the strictest limit you will meet, or carry a compressible soft carrier.
- Keep your pet’s standing height in mind — an 11-inch-high carrier means a pet taller than about 10 inches at the shoulder cannot stand up. Buyers commonly find that a dog over about 10 pounds is probably too tall to stand up in an 11-inch standard carrier.
What Happens If My Carrier Exceeds the Limit?
Carriers are measured at check-in and at the gate. If your carrier does not fit the gauge or the under-seat space, you may be asked to pay a fee, move your pet to cargo (where available), or rebook. The practical rule: a soft-sided carrier can flex to fit, but it must still fit fully under the seat in front of you with no part blocking the aisle. When in doubt, size down — a smaller carrier that fits every flight beats a larger one you cannot use.
Which Carrier Works on the Most Airlines?
An 18″ x 11″ x 11″ soft-sided carrier is the best single compromise in 2026: it fits United, American, Delta and KLM limits, and most 737 under-seat spaces. It will not fit Allegiant, Frontier or JetBlue height limits (8–8.5 inches), so if you fly those airlines, look for a carrier at or under 17″ x 12″ x 8.5″ with a collapsible top. Our airline-approved carrier range and soft-sided carrier range include models in both size families, and our compliance page lists the documentation we can provide with wholesale orders.
How Do You Measure Your Carrier Correctly?
Use a rigid tape measure and measure the carrier’s maximum outer dimensions while it is fully expanded: length from the longest point, width across the widest point, and height from the bottom to the top of the frame — handles and wheels usually do not count, but confirm with the airline. If the carrier has a rigid base and a collapsible top, measure the height with the top fully extended, because that is what a gate agent will check. For soft-sided carriers, compare the label or product page dimensions with your own measurement; a carrier advertised as “airline approved” lists the largest airline it fits, not every airline.
Frequently Asked Questions
Is there one carrier size that works on every airline?
No. Heights range from 8 inches (Allegiant, Frontier hard-sided) to 11 inches (American, Delta soft-sided). An 18 x 11 x 11-inch soft carrier fits most mainline US carriers but not 8-inch-height airlines.
Can soft-sided carriers be slightly larger than the limit?
Some airlines (American, United) state soft-sided carriers may be slightly larger if they still fit under the seat without excessive collapsing, but Frontier, Allegiant and JetBlue measure strictly. Always treat the published limit as the maximum.
Does the carrier count as my carry-on?
On most airlines (JetBlue, Alaska, American, Delta) the pet carrier counts as your carry-on or personal item. Check the fare rules for your specific booking.
Can two pets travel in one carrier?
Some airlines allow two pets of the same species in one carrier if they both fit comfortably (Southwest, Allegiant, Delta in limited cases). Most allow one pet per carrier per passenger.
Need a carrier that fits your airline’s limit?
Email pet@batelipet.com or WhatsApp +86 133 8657 5871 — we’ll help you pick the right size for your route.