While this article paints a charming picture, I have sat next to a large German Shepard dog that used both the owner's and my leg room, a terrier that peed on my shoe and two hamsters stuffed in a shirt.  You can go on line and pay for an emotional support animal certificate.  Travelers, like myself, have allergies to cat and dog dander, which is dismissed by the airlines.  Birds carry a wide range of parasites and are vectors for illness - bird flu.  Many flu strains originated in China as the rural farmers live above pigs and ducks.  This is totally out of control.