Whenever I was in meetings at MS with people who were passing on information directly from the man, they would always refer to him as Bill. I never heard his last name mentioned once. "Bill told us he spent $400m on this. Bill wants his money back."

If you are also called Bill at Microsoft, this might have been confusing.

At Pixar, Steve Jobs was always just Steve, never Mr. Jobs. That was also true of his other companies I believe. After I left Pixar, I was accused of named dropping when I kept referring to him as Steve and I had to change to calling him Mr. Jobs or just Jobs.

Yeah, ok, I could assume that from the gp's post, but what about answering my question directly? How do you address him at the airport, if you have no connection whatsoever? IDK why, maybe you wanna ask him some question, or take an autograph, or you see that he just dropped a wallet, whatever. Will it be "Hey, Bill" or "Mr. Gates"?