Are you eager to know about frontier airlines ? The pet carrier needs to be roomy enough for your pet to move about naturally while standing, sitting, and lying down within frontier airlines pet policy .The only animals that can fly internationally are dogs and cats. You must take steps to ensure that you abide by all applicable laws, customs procedures, and other governmental restrictions of the nation, state, or territory to which the animal is being transported. The carrier for your pet must fit under the seat in front of you.