WASHINGTON, Dec. 2 (Xinhua) -- Under a new regulation issued Wednesday by the U.S. Department of Transportation, airlines will no longer consider emotional support animals as service animals, limiting dogs as the only type that can fly with travelers for free.

In a revision to its Air Carrier Access Act, the department "defines a service animal as a dog, regardless of breed or type, that is individually trained to do work or perform tasks for the benefit of a qualified individual with a disability," it said in a statement.

According to the department, the revision is partly due to "disruptions caused by requests to transport unusual species of animals onboard aircraft," and increasing incidents of travelers "fraudulently representing their pets as service animals" to avoid charges for transporting pets.

Most service animals are dogs, while passengers are growingly taking various animals onboard for "emotional support," including cats, pigs, miniature horses, hamsters, and even peacocks.

With the new rule, airlines are allowed to recognize emotional support animals as pets, rather than service animals.