The crash happened about yesterday at the Stevens Point Municipal Airport. Police say the plane was performing aerial manoeuvers when it went down in a wooded area about 300 metres east of the airport runway.
The pilot's name hasn't been released.
Police ended the show and secured the scene. The Federal Aviation Administration and National Transportation Safety Board will conduct an investigation.
Melvin Burskey of Neenah was at the show. He tells Stevens Point Journal Media he couldn't believe what he saw. He says there was a puff of smoke and then the plane went down.
The air show lineup was to include aerobatic performances and World War II aircraft displays.