According to the new Department of Transportation rules, animals should be allowed on flights if they are used for 'emotional support' by their owners.
However, transportation officers would have to determine whether the animal is permitted on the plane by running through a list of guidelines which are part of a draft manual on equality for disabled people traveling on commercial passenger planes.
"A passenger arrives at the gate accompanied by a pot-bellied pig. She claims that the pot-bellied pig is her service animal. What should you do?" The department manual states.
The manual gives guidelines to determine if they are service animals. Miniature horses, pictured, can help visually-impaired passengers.
According to the new guidelines airline employees should enquire about how the animal aids the passenger and what training it has had.
If the employee has doubts that the animal is a service animal, they can ask for further verification or call a Complaints Resolution Official, the ruling says.
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Service animals help perform some of the tasks that people with a disability have difficulty with or cannot perform for themselves.
Pot-bellied pigs, which can weigh upto 300 lbs, are favoured service animals for people allergic to dogs. They are intelligent companions and attuned to dangerous situations.
Miniature horses work as guide animals for the blind and visually-impaired. They are more cost-effective than guide dogs as their life spans are longer, around 30-40 years. They are also chosen for their calm natures, excellent eyesight and stamina, according to the Guide Horse Foundation.
"Finally, if you determine that the pot-bellied pig is a service animal, you must permit the service animal to accompany the passenger to her seat provided the animal does not obstruct the aisle or present any safety issues and the animal is behaving appropriately in a public setting," the manual adds.
Pot-bellied pigs can grow as large as 300 pounds. They can be trained to open and close doors and use a litter box.
"They seem to have a sense if the owner is not feeling well to stay by them," said Wendy Ponzo, from the North American Potbellied Pig Association.