August 14, 2018 7:38 PM EDT

Southwest Airlines will allow only dogs and cats on board their flights as emotional support animals in an update to its service animal policies, the company announced Tuesday.

Under Southwest’s new policy, which goes into effect Sept. 17, passengers are permitted one emotional support animal per customer and the animals are limited to only dogs and cats that must remain in a carrier or be held on a leash at all times, according to a statement.

Passengers who want to travel with an emotional support animal must present a note from a doctor or mental health professional on the day of departure. Southwest noted in its statement that service animals trained to assist someone with a disability are still permitted — these animals include miniature horses, as well as cats and dogs.

“Unusual or exotic animals” will not be allowed on flights, Southwest said.

Southwest is the latest airline to introduce restrictions to its service animal policy following an uptick in people attempting to board planes with a variety of animals. In January, United Airlines barred a woman from bringing on board an “emotional support peacock.” United, Delta and American Airlines have each cracked down on support animals this year.

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