No arbitrary refusals allowed — Airlines must accept your legitimately trained service dog under the Air Carrier Access Act (ACAA)—but yes, they can deny boarding under specific, limited circumstances outlined by the U.S. Department of Transportation (DOT) under the Air Carrier Access Act (ACAA).
Airlines must recognize a dog as a service animal if it is individually trained to perform tasks for a person with a disability. They cannot deny based on breed, size alone, lack of vest/ID, or speculation. No changes to these core rules as of late 2025.
Permitted reasons for denial (per official DOT guidance):
The dog poses a direct threat to health/safety (e.g., aggressive behavior like biting, excessive barking, lunging, or jumping on people).
The dog causes significant disruption in the cabin or gate area.
The dog is not under control or not housebroken (e.g., urinates/defecates inappropriately).
The dog is too large to fit safely in your foot space without blocking aisles/emergency exits (airlines must accommodate if possible, e.g., bulkhead seating).
Required DOT forms are not provided (Service Animal Air Transportation Form; Relief Form for 8+ hour flights).
The destination country prohibits the dog (international flights only).
If denied, the airline must provide a written explanation within 10 days. You can file a complaint with DOT.
Quick Tips to Avoid Problems
Submit DOT forms early (ideally 48+ hours ahead)
Arrive extra early and use airport relief areas
Ensure flawless public behavior
Know your rights and politely request a Complaints Resolution Official (CRO) if needed
Preparation makes issues rare—experienced handlers say it's almost always straightforward