Airlines are imposing stricter rules.

"Emotional support animals" are not the same thing as trained service animals, and airlines are starting to take note.

There's been a trend of people taking their emotional support animals into airplane cabins and other places where pets aren't allowed, Business Insider reports. In many cases, people are easily able to get a letter from their therapist saying they need an emotional support animal, even when the therapist hasn't met the animal. Some websites will provide the designation for about $70.

But lately there's been an uptick of issues caused by such animals on flights, at least with Delta, Business Insider reports. Problems have included urinating and defecating, along with biting.

Emotional support animals don't have the extensive training that service animals get to help with with diasbilities such as blindness. The federal government has stated that "dogs whose sole function is to provide comfort or emotional support do not qualify as service animals under the ADA."

Delta recently "started requiring anyone flying with an emotional support pet to sign a waiver stating that the animal can behave on a flight" and imposed other restrictions, as well, Business Insider reports. United Airlines has implemented a similar policy, ABC News reports

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