The U.S. Department of Transportation has clarified which service animals can't be banned from airplanes, and miniature horses are in luck. 

Service animals on planes has been a hot topic, especially when the animal is a little exotic (an emotional support peacock was famously denied entry on a United Airlines flight last year). To curb some of the debate, the U.S. Department of Transportation clarified which common service animals should almost always be allowed. 

"With respect to animal species, we indicated that we would focus our enforcement efforts on ensuring that the most commonly used service animals (dogs, cats, and miniature horses) are accepted for transport as service animals," the department said in an issued statement. 

The statement clarifies that animals outside of dogs, cats and miniature horses must be accepted or denied flight on a case-by-case basis. Only snakes, reptiles, ferrets, rodents and spiders can be categorically banned by an airline. 

Airlines are also not permitted to demand proof of training or certification for an animal unless a "threat analysis" is taking place. 

While they aren't as common as dogs, miniature horses are known to make great service animals. Miniature horses should not exceed 34 inches in height and weigh 70 to 100 pounds. 

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