Maybe someone doing some sort of IFR training / practice? I used to grab the proverbial "$100 hamburger" (it was actually breakfast) there all the time and there were always folks practicing approaches / holds / etc. there - they have a manned tower to work with (at least they used to!). That airport has a good restaurant with a ramp that is jammed up with airplanes on Saturday and Sunday. It used to be really cool to fly in there when the NASCAR / Indy crews were in town to see all of their private jets lined up.