Companies do, technically, everything to customers feels special and have the best experience possible. On the other side, customers have their very beloved pets, that are literally family members and very important in their lives. It's common to see companies offering top quality services to pets, so don't be surprised if you see the term PAX associated with a pet.
There are hotels just for pets, where humans can’t check-in (unless the person wanted very much and negotiate it), and this kind of business is old news.
Technically, pets occupies a space, have names, documents, needs authorization to enters on a lot of countries, have needs to be served, everything to be classified as a PAX, but, of course, biologically they are not humans, so the needs and expectation (can we say that pets also have?) are completely different.
Pets can have identification documents, vaccines, and needs the authorization to enter in most countries. There are a lot of pet-friendly hotels available to book on GDS. Photo by Kristin Lopez.
If a pet is on the system as PAX or not, it’s a marketing decision.
The point is: traditional travel information systems that control and distribute services, like GDS, doesn’t classify pets as PAX. Pets doesn’t appear on traditional PNR. But, of course, no one can guarantee that this will never happen. The travel industry evolves, hospitality services are becoming more complexes, and companies systems and processes follow it.