When Coco was a puppy we went away for a weekend and boarded her. She would not eat, or come out of her kennel. Maybe flashbacks of the days at the Humane center where we adopted her, LOL. I vowed to NEVER leave her behind again. I didn't. She goes everywhere with me. When my son began working as a pilot he told me about a trick to get her aboard an aircraft cabin. I had to fill out some paperwork (a one time deal) to have her classified as a 'comfort dog'. My doctor, a close friend went along with it and signed off on the paperwork. Now, because of my "Medical Condition" I must fly accompanied with my "Comfort Dog." It is much like a Seeing-Eye Dog, they cannot be legally denied entry anywhere humans can go. It works. They MUST be WELL disciplined though. I have flown many times with Coco. She is old now and no longer likes traveling on long trips.