If you think that air travel has gone to the birds, it has -literally.

We're talkin' turkey, as in that big Thanksgiving bird, one of which recently was spotted aboard a Delta flight acting as a "support animal," and that's causing a flap over how passengers are using, and abusing, comfort animal rules.

So how can a turkey get on a plane?  Simple.  The passenger provided proper documentation proving the fowl was indeed their emotional support animal, so Delta let the bird on board, and even gave it its own seat.

Reddit user biggestlittlepickle posted the picture, saying that his neighbor, a flight attendant, took this snapshot of the poultry on a plane. unclelimpy, another Reddit user who is friends with the Delta pilot on that flight, followed with another shot of the turkey receiving VIP treatment as it was rolled through the airport on a wheelchair. It even looks like it was enjoying the ride.

Turkeys aren't the only animals used as emotional support animals on flights.  Horses, pigs and--yes, dogs are regularly used.

In 1986, Congress passed the Air Carrier Access Act, allowing service animals to fly on planes and ensuring they can't be removed simply on the grounds that other passengers object. That turkey, or other emotional support animals, requires documentation from a mental health professional. It can't walk about the cabin and can't do their business during the flight (after 8 hours the animal's owner must plan for the clean disposal of waste), something that must be a written guarantee from the human passenger. They also can't block aisles or take up seats near the emergency doors.

“When I saw that turkey on Twitter, I thought here we go.”

It's good to know that Delta and other U.S.-based carriers prohibit unusual service animals, such as snakes and other reptiles, ferrets, rodents, and spiders, as written in the federal guidelines of The Air Carrier Access Act. While Delta prohibits farm poultry, it allows domestic birds, and the turkey, well --apparently is a domestic bird.

In a statement to USA Today, Delta said by letting the turkey fly, they complied with the Air Carrier Access Act. "While we can't always accommodate all pets, Delta employees made a judgment call based in part on extensive documentation from the customer. We review each case and make every effort to accommodate our customers's travel needs while also taking into consideration the health and safety of other passengers."

Travel expert George Hobica, president of the website Airfarewatchdog.com, says these animals are all well and good until something happens.

"The problem with animals of any kind on planes, of course, is possible allergic reactions by other passengers and the possibility that an animal will bite a crew member or another passenger (there have been instances of this happening) or have an accident on the plane, perhaps even forcing an emergency landing if it's bad enough and passengers become ill as a result."

More of a concern is the growing trend of passengers faking emotional support needs and gaming the system to get around paying exorbitant pet fees.  Service animals are free, while shipping pets can cost hundreds of dollars.

SOAR president Captain Tom Bunn, a former commercial pilot who now helps people manage their fear of flying, says it's all too easy to get a therapist to write a note. And websites are popping up that provide emotional support vests and necessary letters for fees ranging from $59 to $200.

"Any therapist can sign off on any kind of animal," he said.  "Science has proven that when dogs look at you with total devotion, it produces oxytocin, a hormone that shuts down the fear mechanism.  The turkey, I don't think so."

Bunn rarely uses dogs or other support animals in his therapy, opting instead for visualization techniques that would bring on the flow of oxytocin.

He says support animals do help for jittery fliers, but when the system gets abused, it's not good for anyone.

"When I saw that turkey on Twitter, I thought here we go," he said. "Some people are going to very annoyed that they paid several hundred dollars to fly with a turkey."

It's likely airline executives feel the same way. But airlines face fines as high as $150,000 for refusing requests for legitimate support animals, and as those requests increase, so does the threat of a lawsuit.

According to Bunn, until the Department of Transportation changes guidelines, there's only one solution.

"The airlines and everyone on board will have to live with it,"says Bunn.