Does frontier airlines allow petsare allowed on Frontier Airlines. Small dogs, cats, guinea pigs, rabbits, hamsters, and housefowl are permitted in the cabin as long as they fit in a carrier under the seat in front of you. The pet has to remain in the carrier the entire flight. International flights are pet-free, and each one-way trip has an additional fee. On Frontier Airlines, pets are not allowed to travel as checked baggage or cargo. As long as they abide by the airline's rules, service animals are welcome without incurring additional fees.