None of that allows him to refuse a direct order to leave private property.

I actually agree with you, but what I find most annoying about this situation is that when a company begins to publically sell shares of its stock it should cease to be considered "private property. Who is to say the doctor doesn't own shares in the company and you're kicking him off a plane that he partially owns? Granted any percentage of the company that he owns would be so small that it's pretty inconsequential, but there's an important distinction to be made when calling this public or private. And if $800 wasn't enough to sway him into arriving a day later, then theoretically he could place a purchase order for $800 worth of shares in United airlines and order anybody else on that plane off of his private property. Do you see the problem with treating publically traded companies (especially in the technology age) as private property? Even for a company like United Airlines that is only trading 3.24% of their company publically split up into 304 million shares among 630 people, if the public owns the company or part of the company, then how does it still get the benefits of truly private business which hasn't opened themselves up to potentially 304 million investors?