PSDs are not required to wear a vest. Staff may never ask a disabled person to have their service dog demonstrate its task.

That would depend on whether your airline allows dogs that large to board the cabin as a pet.

You do not need a certificate for an emotional support animal. An ESA letter is sufficient documentation to prove that you own an emotional support animal.

ESAs are unfortunately no longer accepted on flights. Psychiatric service dogs are still allowed to board the cabin if you submit the DOT’s Service Animal Air Transportation Form to the airline in advance. You can read more about PSDs here: https://esadoctors.com/how-to-get-a-psychiatric-service-dog-letter/

There’s no registry for the ESA, you only need the letter and if the airline requires it, the vet issued health certificate dated within 10 days of travel.

It depends on the airline, I just flew on Delta and there was a Labradoodle. Even if you can’t sleep and have taken prescriptions like Ambian, that is covered under an ESA letter and most airlines take the letter from regular doctors. (each airline specifically says “medical, therapeutic, psychological doctors”