Say goodbye to seeing peacocks in the airport. The government is proposing tightening rules around what kinds of support animals passengers are permitted aboard a plane.

Emotional support animals would no longer be considered service animals under the new airline rules, proposed Wednesday by the Department of Transportation.

The proposed rules would define a service animal as "a dog that is individually trained to do work or perform tasks for the benefit of a person with a disability," eliminating cats and miniature horses from the category.

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Airlines would not be required to acknowledge emotional support animals under the new rule. They would also be able to limit the number of service animals to two per passenger, and to require that an animal fit within its owner's foot space on an airplane.

Carry-on pets that fit underneath an airplane seat would still be allowed.

The new rules are designed to crack down on passengers traveling with unconventional pets like peacocks, possums or snakes. They are designed to "[reduce] the likelihood that passengers wishing to travel with their pets on aircraft will be able to falsely claim their pets are service animals," the DOT said in a statement.

DOT officials said they eliminated miniature horses as service animals because they are less flexible than dogs and space could be an issue, adding that cats are typically emotional support animals. Officials also said that they considered including other animals such as monkeys, but ruled them out because of their disruptive behavior.

The new rules would also bar the current practice by many airlines of requiring animal owners to fill out paperwork 48 hours in advance, the Associated Press reported. However, airlines could still require forms documenting an animal's health and good behavior.

The airline industry group Airlines for America cheered the move, saying the growing number of emotional service animals in flight "has led to an increase in incidents by untrained animals threatening the health and safety of passengers, crew and passengers with disabilities traveling with legitimate service animals," according to a statement.

The Association of Flight Attendants, which represents 50,000 workers at 20 airlines, called the proposed rule "welcome news."

"The days of Noah's Ark in the air are hopefully coming to an end," Sara Nelson, the union's president, told the Associated Press, adding that untrained pets had hurt some of her members.

According to the AP, Southwest Airlines handles more than 190,000 emotional support animals per year. American Airlines carried 155,790 emotional support animals in 2017, up 48% from 2016, while the number of checked pets dropped 17%. United Airlines carried 76,000 comfort animals in 2017.

The public has 60 days to comment on the rule, after which the DOT will come up with a final rule.

Airlines have independently been tightening restrictions on traveling with animals. Delta has banned animals from flights longer than eight hours, while United Airlines requires paperwork attesting that the animal is vaccinated and trained to behave in public.

CBS News' Kris Van Cleave and The Associated Press contributed reporting.