Comfort animals onboard commercial airline flights have become something of a joke in recent years, as flyers have taken advantage of notoriously loose restrictions to bring all manner of pets with them in the passenger cabin.

The idea of comfort animals seems to have gained currency among military veterans returning home from war zones with post traumatic stress disorder (PTSD). An emotional support animal was often prescribed to help ameliorate the symptoms. As PTSD became recognized as an increasingly more common condition, affecting people in many walks of life, comfort animals too proliferated. And not just dogs and cats.

Today there are websites like US Support Animals that advertise “Fly with your animal in the cabin of an airplane at not cost” and provide an easy roadmap for certifying virtually any creature as an emotional support animal. Prices range from $99 to $299 for the service.

It was only a matter of time before some airline or regulatory body stepped up and imposed some order on the system. That time has come, and the airline is Delta.

Related: Should Airlines Get Rid of Reclining Seats? This One Is

Beginning on March 1, according to today’s announcement, Delta will impose new requirements on passengers wishing to have their support animals accompany them onboard Delta flights.

Delta Air Lines is taking steps to further protect its customers, employees and service and support animals by implementing advance documentation requirements for those animals. This comes as a result of a lack of regulation that has led to serious safety risks involving untrained animals in flight.

According to Delta, the airline currently carries around 700 support animals every day, and has experienced an 84 percent increase in reported animal incidents in just the past two years. “The rise in serious incidents involving animals in flight leads us to believe that the lack of regulation in both health and training screening for these animals is creating unsafe conditions across U.S. air travel.”

So, when the new rules take effect, Delta flyers will have to comply with the following in order to take their emotional-support animals with them in the passenger cabin:

• Show proof 48 hours in advance of the animal’s health or vaccinations
• Provide a doctor or mental health professional’s letter
• Provide a signed document confirming the animal “can behave”

Delta also states that it will not accept “exotic or unusual” support animals, including hedgehogs, ferrets, insects, rodents, snakes, reptiles, amphibians, goats, chickens, and any animals with tusks, horns, or hooves.

So even if all the proper documents can be obtained, Delta passengers can rest assured that they won’t find themselves flying cheek-by-jowl with Esther the Wonder Pig.

Reader Reality Check

Is this a sensible step on Delta’s part, or is it overreach?

After 20 years working in the travel industry, and almost that long writing about it, Tim Winship knows a thing or two about travel. Follow him on Twitter @twinship.

This article first appeared on SmarterTravel.com, where Tim is Editor-at-Large.