The airline is required to allow the animals as provided for under the ACAA.
Below are the requirements for an emotional support animal from the
United web site. They do have to submit the documentation in advance and United contacts the mental health care professional to verify. It isn't left to the gate agent to validate.
Emotional support and psychiatric assist animals
Emotional support and psychiatric assist animals are also accepted in cabin for qualified individuals with a disability if certain documentation requirements are met. Additional documentation may also be required for an animal traveling to an international destination. Please note that not all international destinations allow the entry of animals, and restrictions vary by country. Customers should contact the appropriate consulate or embassy to make sure that all necessary procedures are followed.
An animal should sit at the customer's feet without protruding into the aisles to comply with safety regulations. Customers may elect to use an approved in-cabin kennel for smaller animals. Exit row seating is prohibited. Refer to the U.S. Department of Transportation 14 CFR Part 382 or contact United for additional information.
Customers traveling with an emotional support or psychiatric assist animal must provide a minimum 48-hour advance notification to the United Accessibility Desk by 1) calling 1-800-228-2744 from within the United States or Canada, or from elsewhere calling the United Customer Contact Center and asking to be connected to the Accessibility Desk and 2) submitting the required documentation by fax (1-872-825-0208) or email (
[email protected]). The Accessibility Desk must receive and validate the required documentation prior to the time of travel. Verification of documentation will include United contacting your mental health care professional. If we are unable to validate the documentation or if the advance notification is not given, customers will be required to transport the animal as a pet, and pet fees will apply.