I am a retired K-9 handler. It does not take a lot of experience with dogs to tell which ones are service/emotional support animals and those that are not. The airlines need to standardize their polices about allowing 'any' pet on the plane just because the patron 'wants' their pet with them. Very annoying to other patrons who are not comfortable around dogs / animals.
A valid certificate from an accredited agency with a phone number available to confirm the animal's status as a service / support animal would at least be a minimum. Airline personal taking the time to actually check for the animals status would actually deter most fakes.
Airlines should take this step in order to lessen the animal anxiety of passengers. Flying has it's own stressors. Additional stress from an unruly animal and the obnoxious attitude of the owner is an unacceptable and avoidable problem.
Lakeside