By Marnie Hunter and Gregory Wallace, CNN

(CNN) — Airlines don’t have to treat emotional support animals as service animals, a new rule says.

The US Department of Transportation rule announced Wednesday states that “carriers are not required to recognize emotional support animals as service animals and may treat them as pets.”

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Air carriers are also permitted to limit service animals to dogs.

The final rule on Traveling by Air with Service Animals defines a service animal as “a dog, regardless of breed or type, that is individually trained to do work or perform tasks for the benefit of a qualified individual with a disability, including a physical, sensory, psychiatric, intellectual, or other mental disability.”

Airlines have asked DOT to regulate this issue in part over their concern that passengers were fraudulently passing off their pets as the more loosely and fee-free category of emotional support animals.

Flying with a small pet inside the cabin can cost $125 or more each way on US airlines.

The new rule was also prompted by an increase in service animal complaints from passengers with disabilities, a lack of clarity around the definition of “service animal,” misbehavior by emotional support animals and disruptions caused by “requests to transport unusual species of animals onboard aircraft,” according to the DOT.

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Pigs, peacocks and other unexpected animals have previously flown as emotional support animals.

The new rule allows airlines to require passengers traveling with service animals to fill out and submit a DOT form “attesting to the animal’s training and good behavior, and certifying the animal’s good health.”

Approximately 15,000 comments were received in response to a notice of the proposed rule posted in the Federal Register in February 2020, according to the DOT.

Those comments were taken into account in drafting the final rule.

The rule will go into effect 30 days after it is published in the Federal Register. The publication date has not been set.

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