From a Department of Transportation publication offering Guidance Concerning Service Animals in Air Transportation:
Ask about the airline’s policy on advance seat assignments for people with disabilities. For instance: (1) should a passenger request pre-boarding at the gate? or (2) should a passenger request an advance seat assignment (a priority seat such as a (bulkhead seat or aisle seat)) up to 24 hours before departure? or (3) should a passenger request an advance seat assignment at the gate on the day of departure?
Although airlines are not permitted to automatically require documentation for service animals other than emotional support animals, if you think it would help you explain the need for a service animal, you may want to carry documentation from your physician or other licensed professional confirming your need for the service animal. Passengers with unusual service animals also may want to carry documentation confirming that their animal has been trained to perform a function or task for them.
If you need a specific seat assignment for yourself and your service animal, make your reservation as far in advance as you can, and identify your need at that time.
You may have to be flexible if your assigned seat unexpectedly turns out to be in an emergency exit row. When an aircraft is changed at the last minute, seating may be reassigned automatically. Automatic systems generally do not recognize special needs, and may make inappropriate seat assignments. In that case, you may be required by FAA regulations to move to another seat.
Arrive at the gate when instructed by the airline, typically at least one hour before departure, and ask the gate agent for pre-boarding -- if that is your desire.
Remember that your assigned seat may be reassigned if you fail to check in on time; airlines typically release seat assignments not claimed 30 minutes before scheduled departure. In addition, if you fail to check in on time you may not be able to take advantage of the airline’s pre-board offer.
-If you have a very large service animal or multiple animals that might need to be transported in the cargo compartment, contact the airline well in advance of your travel date. In most cases, airlines cannot insist on advance notice or health certificates for service animals under the ACAA regulations. However, it is very useful for passengers to contact the airline well in advance if one or more of their service animals may need to be transported in the cargo compartment. The passenger will need to understand airline policies and should find out what type of documents the carrier would need to ensure the safe passage of the service animal in the cargo compartment and any restrictions for cargo travel that might apply (e.g., temperature conditions that limit live animal transport).
If you are having difficulty receiving an appropriate accommodation, ask the airline employee to contact the airline’s complaint resolution official (CRO). Part 382 requires all airlines to have a CRO available during all hours of operation. The CRO is a resource for resolving difficulties related to disability accommodations.
Another resource for resolving issues related to disability accommodations is the U.S. Department of Transportation’s aviation consumer disability hotline. The toll-free number is 1-800-778-4838 (voice) and 1-800-455-9880 (TTY).