Airline-approved dog carriers must fit under the seat in front of you, and exact dimensions vary by airline and aircraft. As a general guideline, most U.S. airlines accept soft-sided pet carriers around 17–18 inches long, 10–12 inches wide, and 8–11 inches high. Because soft-sided designs can flex slightly, airlines often allow a bit of height variance as long as the carrier compresses to fit fully under the seat.
Beyond size, carriers must be well-ventilated, secure, and comfortable enough for your dog to stand up, turn around, and lie down naturally. Airlines also set weight limits (commonly 15–20 lb total including your pet and the carrier), and your dog must remain in the carrier for the duration of the flight.
How to choose the right size:
Pro tip: Seat spaces can differ by row and aircraft. If possible, select a window or middle seat, which often has more consistent under-seat clearance than some aisle seats. Always confirm details with your airline 48–72 hours before departure.
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It depends on your airline and aircraft. Compare your carrier’s dimensions to the airline’s under-seat size limits and choose a soft-sided model that can flex slightly to fit fully under the seat.
TSA doesn’t set carrier sizes. Size limits are determined by airlines. TSA only requires you to remove your pet during security screening while the empty carrier goes through X-ray.
For in-cabin travel, United requires a ventilated carrier that fits fully under the seat and allows your pet to stand and turn. Check United’s current size and weight limits for your specific route.
