JetBlue wants proof that your miniature ponies or other emotional support animals are really for emotional support before they are allowed on a plane.

The airline became the latest carrier to tighten its policy regarding emotional support animals traveling on planes when it laid out the new rules on Tuesday. Airlines in recent years have seen a spike in the number of animals that are traveling as emotional support pets, which are not required to be crated in the cabin and can ride along for free.

JetBlue (JBLU) said in a statement that the policy change for emotional support animals "follow a dramatic increase in industry incidents involving emotional support animals that haven't been adequately trained to behave in a busy airport or the confined space of an aircraft."

The airline said this "creates health and safety risks for customers, crew members and other service or support animals."

Emotional support animals help people with emotional, psychiatric or anxiety issues, including veterans with PTSD. They're different from service dogs that help people with blindness and other disabilities. JetBlue didn't change its rules for service animals.

Starting on July 1, the airline will require passengers bringing along an emotional support animal to complete three documents at least 48 hours in advance of the trip.

Related: American Airlines tightens policy on emotional support animals

The documents include verification from a mental or medical health professional that says the animal is really for emotional and psychiatric service, a veterinary health form for the animal, and a liability form that that says the animal is "trained to behave appropriately in public." Owners are responsible for injuries to others or damage to property.

The previous policy only required one document confirming the passenger's mental health requirements for an emotional support animal, according to a JetBlue spokesman.

Only cats, dogs and miniature horses are allowed on-board under the new policy. Hedgehogs, ferrets, rodents, snakes, spiders, reptiles and animals with tusks were have long been banned by JetBlue.

The change comes amid reports of animals brought on planes attacking passengers and other service animals. Delta says animal incidents on its planes increased by 84% last year. In one incident last summer, a man was hospitalized from bite wounds when another passenger's 70-pound dog attacked him during boarding, the airline said.

Similar policy changes have been announced this year by American Airline, (AAL) Delta (DAL) and United (UAL).

American said the number of customers traveling with service or support animals rose more than 40% in 2017. The airline also said that insects, goats and hedgehogs are no longer allowed as emotional support animals.

Taylor Garland, spokeswoman for the Association of Flight Attendants, said the policy changes are necessary.

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"People have been abusing this category of animals -- it's essentially to bring the family pet along," said Garland. "This issue has grown so much over the last few years that it starts to legitimately affect the people who really do need these animals."

Advocates for emotional support animals say allowing the pet on a plane may alleviate stress for the passenger. They have also said the new regulations are putting an unfair burden on people with legitimate emotional disabilities.

"While we appreciate the need of airlines to individually adopt policies that support good decision-making by their employees and safe travel for their passengers, the AVMA looks forward to further collaborative efforts with the airlines and the Department of Transportation to adopt consistent, evidence-based policy that supports the safe travel of these invaluable animals," the American Veterinary Medical Association said in a statement.

Last month, the Department of Transportation said that it's seeking public comment on changing its regulations regarding the transportation of service animals.