I know three people like that.
Two of are now working at my company (one used to work for United, the other for Independence Air). With their thousands of hours of experience, they help us by bringing reality into the new concepts we come up with.
The other, also working with United, has started his own business with his wife, they maintain virtual offices for small businesses.
The two United guys are on an "extended leave of absence" and did it voluntarily.