People who regularly rely on emotional support animals (ESAs) while traveling may soon find it more difficult to bring those animals on a plane. A new rule from the US Department of Transportation says that airlines will not be required to recognize emotional support animals as service animals, and may treat them as pets.

A service animal is officially defined as a dog individually trained to perform tasks for the benefit of a qualified individual with a physical, sensory, psychiatric, intellectual, or other mental disability. Emotional support animals will now no longer receive the protections they were previously afforded, and will be considered by airlines as pets, requiring the owner to pay a fee to bring them aboard.

The new restrictions are the result of an increase in complaints about emotional support animals from passengers. Unlike service animals, emotional support animals don’t need to be specially trained to support physical and mental health to board a plane — but they did require airline-specific paperwork from a mental health professional and up-to-date vet forms.

The Airlines for America trade group applauded the decision. “The Department of Transportation’s final rule will protect the traveling public and airline crewmembers from untrained animals in the cabin,” it said in a statement, “as well as improve air travel accessibility for passengers with disabilities that travel with trained service dogs.”

On the other hand, Certapet, an organization that certifies emotional support animals, has voiced its strong disagreement with the new rule. In a statement, it said, “We at Certapet think this is a great disservice to those facing mental health challenges that get emotional support from their animal. We understand that there have been incidents that have discredited emotional support animals and the service they provide.”