Starting July 1, you will no longer be able to bring your emotional support hedgehog, goat or spider on board an American Airlines flight. The carrier issued new guidelines Tuesday, clamping down on the types of service animals and therapy pets it will permit in the cabin, clarifying a previous policy that allowed passengers to board with any animal, from a pig to a peacock.

Unlike household pets, which are subject to a $125 fee each way on American, support animals fly for free. Federal regulations allow passengers to bring their therapy pets into the cabin, as long as there is documentation from a licensed mental health professional testifying to the passenger’s need. But NBC News found a cottage industry of websites where doctors are willing to write letters certifying that a traveler would benefit from having an emotional support animal, or ESA, during the flight.

The rise in fake ESAs has become a controversial issue for fellow travelers, flight attendants and people with disabilities. In addition to safety hazards, allergy issues and delays, it's unfair for those people who have followed the rules.

“I can spot a fake emotional support animal a mile away,” veteran flight attendant Heather Poole, author of "Cruising Attitude: Tales of Crashpads, Crew Drama, and Crazy Passengers at 35,000 Feet," told NBC News. “It's usually growling or barking at other support animals. That, or it's dressed nicer than its owner.”

American Airlines listed the specific creatures it has banned from the cabin, including amphibians, ferrets, goats, hedgehogs, spiders, sugar gliders, waterfowl, and animals with tusks, horns or hooves. Miniature horses "that have been properly trained as service animals" are an exception to the last rule.

The airline also banned "any animal that is unclean or has an odor."

Additionally, the new restrictions clarify what behavior is acceptable. The animals must be "trained to behave properly in public" and not display "any form of disruptive behavior that can’t be successfully corrected or controlled," including growling, biting or lunging at people.

Rival carriers Delta and United also updated their transportation policies earlier this year, adding a requirement that passengers traveling with service animals or ESAs must book at least 48 hours in advance and submit additional documentation.