Cats do not have the same homing instinct that dogs do. Cats can easily get lost in unfamiliar surroundings. They expand their outdoor territory slowly over time... time that they don't have in a campground. Read the many sad tales in RV forums of those who have stayed beyond their scheduled time at a campground, fruitlessly hoping "kitty" will come home. While you may think they are trained to stay around the trailer, all it takes is a fast squirrel or bird to trigger their instinct to chase... chase so focused on the target that they aren't keeping track of their surroundings.

Ours are literally house cats 100% of the time. They DO get to spend time outdoors, but in a folding cage. I don't recommend a pet door in an Airstream.

I am hopelessly aware of cat's and their limitations...thanx for letting others know.
Unfortunately, I was forgetting that most people on the Forum are fairly "mobile"...and was thinking about it for those, like me, who are living full-time in their RV.
"Bear" is my HOME....and my new kitty will be trained to be indoors for the most part...but, will be allowed to go out and chase butterflies once in a while. I will have a 'cat door' on my 10 x 10 shed too...to allow her the chance to escape. She will also be trained to 1. come like a dog when called, 2. not eat plants; 3, not scratch the furniture; 5, not get up on the table/counters, and to snuggle with me.
AND NO, I don't believe "CAT WASTE" WOULD HURT THE BLACKWATER HOLDING TANK ANYMORE THAN HUMAN WASTE WOULD. I'd be interested in hearing any experiences on this otherwise. I think RV holding tanks are limited only by what is 'biodegradable" or not.

A cat door can be purchased at any hardware store, and I am just installing it where it won't have to go through the 'fuselage' of the rig.