Well Iwon't argue that, except to say that engineers and lawers will call it that to mean the airspace that is not considered navigable. You can look it up on the web and see the word used in exactly the way I intend.

Oh, Ichage my mind. Non is latin for NOT. It is used in front of words and can be taken as literally not navigable. When taken in the legal context it means it is illegal to navigate through. Not that it would be physically impossible to do so.