United, Delta Change Rules for Emotional Support Animals

New rules on flying with emotional support animals kicked in today for United Airlines and Delta Air Lines, following a string of controversies that included a peacock.

The airlines have seen an increase in those service animals and will now require information about the animal's health, as well as confirmation that it will behave during the flight. Previously, the airlines only called for a note from a health professional about the traveler's need to bring an emotional support animal.

The additional documents must be submitted at least two days before the trip. The new rules will not affect other service animals.

"These measures are intended to help ensure that those customers traveling with a trained service or support animal will no longer be at risk of untrained pets attacking their working animal, as has previously been reported," Delta said in an earlier statement. "Ignoring the true intent of existing rules governing the transport of service and support animals can be a disservice to customers who have real and documented needs."

United did not immediately return a request for comment from Newsweek.

A recent incident with a peacock was one of the more memorable controversies linked to emotional support animals flying on United — or rather, not flying. The airline turned away a peacock at Newark Liberty International Airport in late January, citing the bird's size.

"We explained this to the customer on three separate occasions before they arrived at the airport," United told NBC News at the time. "We know that some customers require an emotional support animal to assist them through their journey."

The Transportation Security Administration's guide on traveling with service animals notes that "unusual animals are evaluated on a case-by-case basis" and those that are too large can be denied.