You don't decide it — a number does. How to measure your pet in five minutes, how to read any carrier's spec, and the test that tells you whether cabin is even possible.
Almost everyone starts in the wrong place: by choosing a carrier.
The right order is the reverse. First you measure the animal. Then you check what your airline allows. And only at the end do you buy the box — if one exists that works, which is exactly what you want to find out before spending anything.
It's a number, and the number is combined weight: the animal plus its carrier, together, on the scale.
Every airline sets a cabin ceiling. If your dog plus their box comes in under that ceiling and the box fits the maximum dimensions, cabin is possible. If either of those fails, there's no discussion and no counter exception: it's the hold, a different airline, or a different plan.
For a real reference — the kind we verified in the article on flying inside Mexico — Volaris publishes a cabin ceiling of 12 kg combined, with a carrier no larger than 44 × 30 × 19 cm. Other airlines set other numbers. The shape is always the same.
You need a tape measure, a wall, and someone to help if your dog won't cooperate. With the animal standing, not sitting or lying down:
A — Length. From the tip of the nose to the base of the tail. Don't include the whole tail.
B — Height. From the floor to the highest point of the head while standing. For dogs with upright ears, to the tips of the ears.
C — Width. The widest point of the body, usually the shoulders or the hips.
Write all three down with the date. A puppy changes them in weeks, and six months from now you won't remember whether they were from before or after.
Airlines publish similar formulas. Volaris, for instance, describes theirs like this: the container's length is the animal's length plus a quarter of it, and the width is double their widest point.
In round numbers, to orient yourself:
That's the smallest box your dog can travel in. It isn't the ideal one: it's the acceptable minimum, and below it the answer at the counter is no.
You now have two sets of numbers: the minimum your dog needs and the maximum your airline allows.
If the minimum fits inside the maximum, cabin is possible. Buy a carrier that lands between the two.
If the minimum is bigger than the maximum, cabin is off the table — and you know that today, at home, rather than on flight day with the box already bought.
That's the whole exercise. Five minutes and a tape measure save you the most expensive scene of the trip.
Don't guess. Stand on the scale yourself, then stand on it holding the carrier with your dog inside, and subtract. It's exact and takes a minute.
Do it with the box you'll actually use, with the blanket and everything else going inside. That's the number weighed at the airport, not the dog alone.
A new carrier is an unfamiliar box. If they meet it on flight day, they meet it on the worst possible day.
Open it at home and leave it open weeks in advance, somewhere your dog already spends time. Let them come and go. Let good, boring things happen in there. It costs nothing and it's the difference between a box and a place.
Your dog's three numbers — length, height, width, with a date — are exactly the kind of detail that's useful twice and gets lost once: you measure for this trip and can't find them for the next.
Today in Maskotis you can register your pet and keep their details and care events there, with dates. What else is worth recording is here.
Measure today. Buy afterwards.
Each airline's dimensions and ceilings change: confirm them on their official site before buying a carrier or a ticket. The Volaris examples cited here are taken from their public page, linked in the previous article in this series.
Maskotis does not give medical recommendations and this article is not a substitute for a veterinary consultation. If you have questions about whether flying suits your pet, that's answered by the person who can examine them. Take them to the vet you trust, or to the nearest clinic — they'll help you there.
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