The final rule still defines psychiatric service animals as service animals, but emotional support animals are no longer considered service animals. The rule allows airlines to limit individuals to 2 service animals, to limit them to animals that fit in the footspace on the plane, to require paperwork be completed regarding the animal’s health and behavior and includes other rules:

https://www.transportation.gov/briefing-room/us-department-transportation-announces-final-rule-traveling-air-service-animals