Discover Southwest Airlines Pet Policy offers an easy and cost-effective way to travel with small cats and dogs on domestic flights. Pets can be carried in the cabin, so they are safe, comfortable, and close to their owners. The requirements for a carrier and the rules on vaccinations are very clear, so it is easy to prepare. However, Southwest doesn't allow larger pets, nor can they be shipped as checked baggage or cargo. That might be the only drawback. But, overall, it is quite reliable for small pet owners.