There was a time when there were no strict regulations concerning aviation. Pilots could go as low as they wished, do the craziest stunts and buzz the audiences. In the twenties there were these fearless flyers called the barnstormers. From a temporary airstrip they amazed the gathered crowds. They buzzed people, wingwalked, jumped from a plane into a car, did aerobatics and in some cases they even played tennis on top of a plane. Some of these barnstormers acted as a group in what was called a flying circus. A term that covers it very well.
As you might notice, many of the barnstormers used a Curtiss Jenny. The explanation for this is quite simple. WWI was just over so there were many airplanes up for sale which made them cheap and a much loved airplane among barnstormers.