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Southwest Airlines limits emotional support animals to cats and dogs. Pigs on no-fly list.
Southwest will limit emotional support animals to one per traveler and the policies take effect Sept. 17.
Passengers, airlines and their crews have complained about allergies, soiled cabins, and biting.
The ease with which passengers can certify their animals for emotional support has raised concerns that some are bringing pets aboard to avoid airlines' in-cabin pet fees.
Southwest Airlines LUV next month will restrict emotional support animals to dogs and cats and require them to travel in a carrier or be leashed, the company announced Tuesday.
The Dallas-based airline is the latest carrier to crack down on the boom in emotional support animals on board commercial flights.
Passengers have pushed the patience of what flight crews, airlines and fellow travelers will tolerate as psychological support, traveling with turkeys, pigs as well as thousands of dogs and cats. United denied boarding to a traveler's peacock she tried to bring on as an emotional support animal earlier this year. US Airways, which merged with American in 2013, once ejected an emotional support pig and its owner after the swine defecated on a flight.
American AAL , Delta DAL , United UAL and JetBlue JBLU issued tighter rules for such animals earlier this year.
Passengers and crew members have complained about allergies, animal aggression, including biting, and soiled cabins. A passenger last year was mauled on a Delta flight by a another traveler's emotional support dog. Airlines have have reported a sharp increase in the numbers of such animals on board, as required documentation for such animals to qualify have been easily attainable online.
Emotional-support and service animals can fly free of charge and without a carrier under the 1986 Air Carrier Access Act.
The Department of Transportation is considering more specific definitions of which animals should be allowed on board. United and American this summer wrote letters to the DOT urging it only permit animals that are specially trained to assist a person with a disability, such as a seeing-eye dog under, to fly for free under that definition. The DOT received close to 4,500 comments on the issue .
In its statement on Tuesday, Southwest noted that psychiatric-service animals, those trained to help those with a mental disability, will still be permitted but said it will only allow dogs, cats and miniature horses in this category while "unusual or exotic animals" such as rodents, ferrets, insects, spiders, reptiles, hedgehogs, rabbits, or sugar gliders will not be accepted.
The changes on Southwest take effect on Sept. 17, the airline said.
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