If you plan to travel with your pet on Southwest Airlines, it's important to know their rules about pet carriers. Only small cats and dogs are allowed to fly in the cabin, and they must stay in a carrier that can fit under the seat in front of you. The carrier should be soft-sided, easy to carry, and comfortable for your pet. It also needs to be secure and have good airflow so your pet can breathe easily. Before your flight, make sure the carrier follows the official Southwest Airlines pet carrier dimensions to avoid any issues at the airport. This way, your pet can travel safely and you can enjoy a smooth trip.