Spirit Airlines pet policy accommodates pets of all sizes inside the cabin, making sure that pets travel along with their owners. Pets are required to be comfortably into a car seat under the seat, and must meet weight and size restrictions. There is a fee per pet and reservations in advance are suggested due to the small space. Documentation such as health certificates could be required. Spirit strives to offer an enjoyable travel experience for pets with a focus on safety and comfort of pet and passenger.