With the increase in animals on flights, airlines have reported more incidents of animals roaming freely around the plane, defecating or being aggressive. Several airlines are taking steps to help ensure that only trained, properly-behaving service and therapy dogs are allowed on flights.

Delta Airlines announced in June that it would no longer allow "pit bull-type" dogs on flights as service and support animals. The policy went into effect July 10. The policy also introduces a limit of one emotional support animal per customer per flight.

According to a Delta press release, the changes are in response to recent incidents in which several employees and passengers were bitten. The company also cites an increase in incidents of animals urinating and defecating on flights. The company gives no specifics about the breeds of the dogs involved.

"The safety and security of Delta people and our customers is always our top priority," said Gil West, chief operating officer, in that release. "We will always review and enhance our policies and procedures to ensure that Delta remains a leader in safety."

Delta flies about 700 service or support animals each day, according to the company. Customers have attempted to fly with snakes, spiders, turkeys and gliding possums as comfort animals.

"The rise in serious incidents involving animals in flight leads us to believe that the lack of regulation in both health and training screening for these animals is creating unsafe conditions across U.S. air travel," said John Laughter, Delta’s senior vice president of corporate safety, security and compliance, when updating the airline's policy in March. "As a leader in safety, we worked with our Advisory Board on Disability to find a solution that supports those customers with a legitimate need for these animals, while prioritizing a safe and consistent travel experience."

United also requires passengers provide vaccination or proof of health documentation 48 hours before a flight (along with the federally-required doctor or therapist's note for emotional support animals).

Beginning Sept. 17, 2018, Southwest Airlines will limit emotional supports animals to only dogs and cats. There can only be one ESA per customer, the animal must be in a carrier or on a leash at all times and the passenger must provide a letter from a medical doctor or licensed mental health professional on the day of departure.For trained service animals, Southwest limits passengers to dogs, cat and miniature horses.

Airlines aren't the only ones cracking down on emotional support animals. Royal Caribbean announced it's banning all emotional support animals from its ships effective immediately for new reservations. "We are updating the policy to differentiate emotional support animals from service animals that are trained to perform a function for a person with a disability," read an email statement sent to the Los Angeles Times. "It is important to us that all our guests enjoy their vacation, which is why we put into practice this new policy."

Defining service and emotional support animals

Dogs can smell fear and stress, and can use that ability to help people with issues such as PTSD. A service dog is one that has been specifically trained for its owners health needs. (Photo: Glynnis Jones/Shutterstock)

The idea of a "service" dog can be fuzzy. Many people use the term, but true service dogs are highly trained to perform specific tasks to help an individual with a disability.

Service dogs are different from emotional support animals, which provide comfort to their owners, but don't require training. The only animal that legally can go to any public place the handler goes is a service dog.

MNN's Jaymi Heimbuch has an in-depth explanation of all the differences and protections offered to service dogs versus emotional support animals.

As Heimbuch points out, there has been a backlash against people who try to pass off their pets as fake service dogs or even questionable emotional support animals. When these pets aren't well trained, incidents like the one Delta cited can occur.

Editor's note: This article has been updated since it was originally published in June 2018.

Mary Jo DiLonardo writes about everything from health to parenting — and anything that helps explain why her dog does what he does.

Airlines crack down on support animals
The types of animals passengers can bring along is changing rapidly.