It's important to know the size of pet carrier Southwest Airlines requirements when planning to travel with your pet for an easy flight. The airline allows only small pets in the cabin, and they have to be properly secured in a seat-underfitting carrier that has been licensed. The carrier needs to be air-tight, leak-proof, and large enough for your pet to stand and turn around without problems. Choosing the right pet carrier size for Southwest Airlines accepts helps keep your pet safe and comfortable while the trip in along with guaranteeing compliance.