The problem with this, of course, it that it's all illegal -- and has been since ADA was passed in 1990...28 years ago.
You simply can't force disabled people to jump through hoops -- it's against the law.
I know it's against the law, and I said so, but laws can be changed, and at this point, they should be. It is time to amend the ACAA and ADA rules about animals for safety reasons.
I am not in favor of the disabled being forced to supply proof of disability; that should stay as is; there is no need to stigmatize PEOPLE in these situations, as people are not likely to bite and usually don't have claws or sharp beaks. Animals, however, are another story, and when it has become obvious that the safety of other passengers (including that of other disabled people, and other service or support animals, I might add) is being compromised, then an amendment to the ACAA/ADA is in order to address this.
If you wish to bring an animal into the cabin of an aircraft, you should have to provide some proof that the animal in question will not pose a danger to other passengers. That would include some certification of vaccinations and a minimum level of training if you are asking for the animal to travel unrestrained.. Otherwise, your Emotional Support Animal should need to be muzzled or stay in a latched container. It is NOT an unreasonable accommodation for passenger safety aboard an aircraft. Disabled persons who have trained SERVICE animals all have documentation for those animals. There are no hoops to jump through in that case. I really don't see how a Supoort Animal should be any different. In most places, if you own a pet you have to register it for a vaccination tag; how is it that much more onerous to also register (with documentation) that it has been trained if you wish to customarily bring it aboard an aircraft?
Most of us pay a tag charge to record our animals' vaccinations. I'm fine with the idea of having physicians sign a state form for recording emotional support status, and having that form give you a waiver of the fee. We do it for disabled parking permits, and that is not considered to be an unreasonable exercise in hoop-jumping.
There have been instances in public transit where trained Service Animals have been attacked by untrained "Support Animals". Surely you can see that this is a situation that those who drafted the law did not foresee, and that it needs to be amended for public safety reasons.
CORRECTION: I'll admit it, I messed up in the paragraph above; by getting my S words confused when trying to type in a hurry. Trained support animals don't generate documentation. What I meant to say was "trained SERVICE animals"; they do have documentation of their training, because there is always a whole lot of paperwork involved in acquiring one. They are scarce and are very expensive to train; so unless you have money to burn and are willing to pay privately for sourcing a suitable animal and having it trained, you are not going to get one unless you go through the hoops of proving that you need one. The human partners of such animals are also required to go through training. (Paws with a Cause estimates the cost of each service dog at $30K)
Let me be clear here: I KNOW WHAT THE LAW PRESENTLY IS with regard to asking for training documentation of service and/or support animals. What I am saying is that due to the proliferation of completely untrained animals being self-identified as service and/or support animals, I strongly believe that for the safety of other passengers, THE LAW NEEDS TO BE CHANGED when it is a matter of such animals being taken on board public transportation vehicles.