Roosters have boarded airplanes. So have turkeys, ducks and monkeys — all in the name of service. These animals allegedly helped their owners stay calm. Never mind that they may have had the opposite effect on nearby passengers.

The "emotional support" designation also helped owners save money — calming, indeed, when airlines charge $125 one way to convey a pet in a carrier under the seat. A friend once told me that she easily obtained a letter from a psychologist so she could fly her tiny dog around the country free of charge.

The mile-high menagerie may be coming to an end. The U.S. Department of Transportation proposed a new rule on Wednesday that would let airlines ban untrained emotional support animals — an entirely different breed, so to speak, from the fully trained service and guide dogs that help the likes of veterans with PTSD and the visually impaired.

Already, airlines have banned certain animals. Alaska Airlines, for instance, prohibits rodents, ferrets and snakes. Delta's list is longer and includes birds, all amphibians and animals with tusks, horns or hoofs, such as goats.

People with legitimate need of a support dog — a veteran, the mother of an autistic child — have told me that the surplus of support animals makes their air travel uncomfortable, as fellow fliers look askance at their dogs. Fliers have been bitten by unrestrained dogs in airports and on planes. Online sites spit out letters qualifying pets as emotional support animals for a fee. It's time to take a look at the issue.

The flying zoo started in 2003, when the Department of Transportation expanded the definition of service animal to include any that lends emotional support. That followed a 1986 law requiring U.S. airlines to permit service animals.

The public has through July 9 to comment on the proposed rule that would limit the flying privilege of service animals to only those that are fully trained. Share your views at regulations.gov (input docket number DOT-OST-2018-0068). Or send a comment by mail to Docket Management Facility, U.S. Department of Transportation, 1200 SE. New Jersey Av., West Building Ground Floor, Room W12-140, Washington DC 20590-0001.

Whether a growl or a purr, let your voice be heard.