I've been in the cockpit multiple times on UA post 9/11, always on the ground. Most of the times I was with my daughter who is fascinated by airplanes. I've got a picture of her in the pilot's seat of an A320, complete with the pilot's hat. And she got to spend the better part of an hour last summer in the cockpit of a 737 asking the co-pilot questions after we diverted to the "other" airport in Houston during stormy weather. The co-pilot in that case was fielding questions from both a four-year-old (mine) as well as a fifteen-year-old who was also fascinated. In all cases the flight crews have been friendly and approachable, and have gone beyond my expectations in making us feel welcome while they are trying to do their jobs.