I have never flown on a flight where a legitimate service animal was present, so I am curious, where exactly does a full size dog lie, without being in the aisle or encroaching on the floor space of the passenger/s next to the owner? And if an encroached passenger were to complain, would the airline side with the animal/owner every time?
Basically, in US, almost any animal can be declared to be “emotional support” and airlines cannot deny that access. This is the most abused rule, the certificates can be bought online and I think some people just put a vest of “Service Animal” on their pets.
Sometimes, responsible owners will buy an extra seat, and I applaud them.
I flew with numerous cases, including internationally as recent as last month (a woman had two small dogs with her). Luckily the plane was occupied only like 1/3 so the issue of encroaching was null.