Regarding the Rock Co. airport, I'm not 100% sure who mans the tower there. I just think it was in the news to make Paul Ryan look bad or something like that. I believe GM (when the plant was still opened) would have parts flown in and they would come through that airport, but I was always aware of the parts/cars that came in by trains. It's not a busy airport at all. The biggest plane that ever landed there (when I was growing up...) was Air Force One or that smaller version of it. Hillary Clinton flew into Janesville during Bill's last year or two in office. Otherwise, military planes would come in occasionally to fuel up. All other planes were privately owned ones.
The Rock Co airport also has an annual airshow in the summer, which is always a blast to watch.