If you've been an airline passenger in, say, the last five years or so, you've likely noticed an increase in the number of passengers carrying emotional support animals.

Dogs, cats, miniature horses. One woman tried to board with a peacock. 

The peacock wasn't allowed, but it did become a social media sensation. Then it died, of non-airline-related causes.

It gets worse. On United Airlines, a passenger tried to board with an emotional support animal that also had its own, second emotional support animal. (Apparently the ark was full.) 

We can keep going. On Alaska Airlines, the airline had to choose between an emotional support cat and a teen-aged, paying customer who was allergic to it. The cat won.

But in the last year or so, there's finally been a big pushback. 

The airlines banded together to try to ask for a government crackdown. (It turns out there's been a big, gaping hole in the law that lets people take animals on airplanes, even when they'd never allowed in other public places.)

Delta laid down the law in January, and then made things even stricter last month. Southwest Airlines decided in August: cats and dogs only. Plus, miniature horses, which sounds kind of crazy but apparently is an occasional thing.

It's easy to make fun of all of this -- and frankly most of the people who absurdly bring absurd animals into this absurd situation deserved to be mocked for their absurdity.

But there has also been violence, and threats of violence. A Delta passenger was mauled by a dog in 2017. And a dog allegedly bit a young girl on a Southwest Airlines flight. 

The airlines say they saw a surge in animals "barking, biting, nipping, growling, and fighting" plus of course, "uncontrolled urinating and defecating."

All of which brings us to the newest change that Delta made last month, and that United announced this week. In short, let's call it the "just because it's cute doesn't mean you can bring it aboard" rule.

The new rules.

  • Dogs and cats only as emotional support animals; dogs, cats and miniature horses as service animals.
  • No animals at all under four months of age, so no kittens and puppies. 
  • No emotional support animals on fights over eight hours.

Delta's restrictions started last month; United's begin January 7.