Airport mystery: How did a monkey end up on a plane to Las Vegas?

LAS VEGAS (KSNV) - An investigation is underway into how a monkey ended up in the cabin of a plane coming to Las Vegas.

TSA agents who are trained to check travelers before they get on planes say the monkey and its owner were properly screened when they left Columbus, Ohio to come to Nevada.

The monkey was an emotional support animal that can travel with its owner. However, there seems to be a lot of confusion about how the monkey got on the plane in the first place.

The animal was on a Frontier Airlines flight Tuesday night. A flight attendant noticed it sticking out of a passenger's shirt.

Frontier Airlines told News 3 the passenger refused to provide paperwork for the animal when asked for it by the flight attendant.

According to Frontier, the monkey's owner broke policy by never telling the airline an emotional support animal was being brought on board.

TSA officials told News 3 they knew about the monkey. They say the animal went through a scanner in Columbus, Ohio and the passenger was holding it.

Frontier Airlines has a different story. Frontier officials told News 3 the monkey was in a duffel bag.

"We've heard all sorts of stories about people with all sorts of animals trying to board airplanes or go to restaurants and to stores, everything from pigs to turkeys, to you name it," said Katie Malatino with Canine Companions.

Malatino said some pet owners are cheating the system to fly their pets for free.

"We're encountering it more and more. People are trying to pass off their untrained pets as service animals," Malatino explained.

News 3 found plenty of websites that offer emotional support animal certifications. One website promised to get your pet registered for less than $70.

"There's just a lack of regulation and oversight of the industry by the government," said Malatino. "When people try to pass off their untrained pets as service animals, it's really a great detriment to people who really rely on their service animals to get around and to live life fully.”