If you rely on a squirrel, hamster, peacock or pig for emotional support when traveling, you might consider new federal guidelines unfair.

After all, they don’t guarantee you’ll be able to get your rodent, bird or swine onto an airplane.

The new guidance, issued by the U.S. Department of Transportation last month, gives greater travel priority to passengers traveling with trained service animals than those with certain emotional support animals.

The guidelines come amid the growing popularity of emotional support animals and the holes in the patchwork nature of federal laws and airline policies addressing their travel requirements.

READ MORE: No More Snakes on a Plane, and Peacocks Are Out, Too

Industry trade organization Airlines for America says the number of emotional support animals, or ESAs, on U.S. airlines surged by 60 percent in 2017 and went up another 14 percent in 2018.

Those compare to much more modest increases of 3.1 percent and 4.7 percent, respectively, in the number of passengers.

Under the Americans with Disabilities Act, service animals are defined as dogs that have been trained to assist people with physical disabilities, such as guide dogs for the blind and visually impaired. (While ADA rules allow for other animals as alternatives to dogs in certain situations, such as cats and miniature horses, canines are the only creatures that can be definitively labeled service animals.)

Emotional support animals, or ESAs, are those that provide comfort to people with emotional or psychological impairments.

The new rules allow the airlines to use their discretion to deny transport to specific animals that could pose a threat to passengers. But the airlines could be in violation of the rules if they refuse transport to specific breeds of dogs trained as service animals or common non-canine species used as service animals.

However, airlines can ban exotic species, such snakes, ferrets, spiders and others.

The new regulations impact only airlines and will have no effect on Pittsburgh International Airport. Brian Stashak, airport vice president of customer and tenant experience, said the airport always has been service animal-friendly.

“As long as the animal is on a leash or in a kennel or cage of some sort, you’re fine [at the airport],” he said.

Under the revised guidelines, airlines are not required to transport emotional or psychiatric support animals unless travelers present medical documentation that the animal is necessary.

Also, while passengers aren’t required to inform airlines they will have a service animal traveling with them, those traveling with emotional or psychiatric support animals must notify the airline in advance.

Airlines are permitted to require animal owners to show proof of vaccinations, behavior and training to see if the animal poses a potential threat to passengers or crew. That requirement comes after a recent incident in which an emotional support dog bit an American Airlines flight attendant severely enough to require stitches.

For transcontinental flights of eight hours or more, airlines can ask for documentation that the animal, if necessary, can relieve itself in a manner that doesn‘t create a mess or sanitation issue. But federal transportation officials offered no suggestions as to how this requirement can be met.

Airlines also can deny transport to a service animal they deem too large or heavy. USDOT also will permit the continued prohibition of transporting service animals younger than four months, as some airlines have done.

As for how the animal is to stay close to its owner in the cabin, “tethering and similar means of controlling an animal … would be reasonable in the context of controlling service animals,” the transportation department stated in a release.

What do the airlines think of the new rules? Southwest Airlines, which transported the most passengers at PIT last year, referred comment to industry trade group Airlines for America. The organization supports the revised regulations, contending it will cut back on the number of unnecessary emotional support animals on flights.

“With over a million passengers bringing ESAs on flights last year, airlines and airports saw a sharp increase in incidents such as biting and mauling by untrained animals,” the organization said in a statement. “The DOT’s guidance is an important step toward addressing this growing problem and ensuring a safer and healthier travel experience for all.”

To see the new regulations in their entirety, click here.