"Emotional support animals... travel free, and restrictions on their size and species are left to the airlines’ discretion."

"They are not required to be caged. And unlike service animals, which undergo extensive training, they require no training."

Their task is to provide comfort to their companions. To serve the needs of the animals and their owners, a cottage industry of websites and doctors advertising documents that certify emotional support animals has emerged....

Carla Black, a psychotherapist in Marina del Rey, Calif., began receiving enough requests for emotional support animal certification that this year she began advertising on her website. For $99, she provides an hour of her time, over the phone or Skype, and a clinical assessment, along with a prescription letter, which is valid for one year.

Ms. Black said in a telephone interview that before she issues a letter she ensures the client is eligible under criteria set by the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition. “I make sure they qualify for depression or whatever, P.T.S.D.,” she said, referring to post-traumatic stress disorder.

I take it that must be covered by an Obamacare-compliant health plan, which must cover mental health.

One more reason to avoid getting on an airplane. I picture myself seated between the lady with a potbellied pig on her lap — his dripping snout overhanging the armrest — and the man who's having a breakdown because he's allergic to pigs.