Passengers wanted 'emotional support' peacock aboard flight. The idea didn't exactly take off.

It's not unusual to spot animals of various kinds at the airport — dogs and cats for the most part. Sometimes animals are small enough that passengers are able to bring them aboard flights.

But when United Airlines employees at Newark Liberty International Airport recently got an eyeful of a peacock — with its own ticketed seat, mind you — that was apparently too much.

According to Live and Let Fly, the argument was made that the colorful bird was expressly there to provide "emotional support" — but United still said no way.

And actually a United Airlines spokesperson told Fox News that the customers in question were informed more than once — even before getting to the airport — that the peacock wouldn't be allowed on board.

"This animal did not meet guidelines for a number of reasons, including its weight and size," United said in a statement to the network. "We explained this to the customers on three separate occasions before they arrived at the airport."

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The news comes on heels of Delta’s controversial crackdown of emotional support and service animals. On Jan. 19, the airline announced forthcoming restrictions in hopes of curbing an abuse of policy and an 84 percent increase in ill animal behavior such as urinating, defecating, biting and attacks on flights.

Effective March 1, Delta’s new rules require those flying with emotional support or psychiatric service animals to submit a veterinarian health form and immunization record to Delta with 48-hours’ notice, Fox News reports. A doctor’s note, signed veterinarian health form, and proof of animal training will additionally now have to be presented before boarding.

Further, as of March, Delta will not allow exotic emotional support animals including ferrets, insects, spiders, goats or animals with tusks or hooves to fly.

When else have emotional support animals on planes made headlines?

An airline passenger was allowed to bring an emotional support pig aboard a flight in 2014 — until the pig began squealing and defecating in the aisle.

“We could smell it and it was a pig on a leash,” a fellow passenger aboard the US Airways flight said. “She tethered it to the arm rest next to me and started to deal with her stuff, but the pig was walking back and forth.”

Another passenger remarked about the pig: "I was terrified."

Flight attendants eventually asked the animal’s owner to exit the cabin, and the owner reportedly did so before takeoff without incident.