This piece originally appeared on Travel + Leisure.
Planning a trip can be stressful—especially when you’re bringing your pet. Not all airlines allow passengers to bring a pet on board, and the ones that do often have very specific guidelines. Some airlines allow dogs, but not cats; others are also cool with rabbits, hamsters, and small birds. (Ferret owners: Aegean Airlines has got your back.)
Not only are airlines particular about which types of pets they allow on board, they also have different rules about the pet’s breed, size, weight, age, and health. Leaving on Jet Blue? You might want to put your pudgy pug on a diet before the trip: the combined weight of the pet and its carrier cannot exceed 20 pounds. On Delta, pets aren’t allowed in first class; if you’re flying Southwest, get to the airport early—a total of six pets are allowed on each flight, and permission is granted on a first-come, first-served basis.