The Frontier Airlines pet policy is as follows:
Effective January 11, 2021, Frontier will no longer accept new bookings for passengers wishing to travel with an emotional support animal.
Domesticated dogs, cats, rabbits, guinea pigs, hamsters, or small household birds are accepted in the cabin on flights within the United States.
The following species are never accepted: Large birds (e.g. parrots, macaws, cockatoos, birds of prey), rodents (including mice, rats, squirrels), beavers, ferrets, reptiles (including snakes), amphibians, spiders, and insects (and please, no lions, tigers, or bears).
Only domesticated dogs and cats may be carried to or from international destinations.
Pets are allowed in the cabin on all domestic Frontier flights, and on international flights to/from the Dominican Republic and Mexico.
Frontier does not accept pets to be checked as baggage.
Taking a pet to a foreign country involves preparation and planning far in advance of your departure date. Requirements for pet travel to a foreign country are set by the destination country. If you are you traveling to another country and bringing along your pet you’ll need to meet the animal health requirements of the country you are visiting.
More information on the Frontier Airlines pet policy