(AP) — A new study by researchers at the University of Kansas shows that air turbulence created by wind energy turbines could pose safety problems for small aircraft.

Tom Mulinazzi, a KU engineering professor, says wind turbines can set up a circular vortex that can roll a small plane if it gets in there. He says the turbines can also increase crosswind speeds above what pilots expect, which can also be dangerous.

The study was done for the Kansas Department of Transportation after the department began hearing more pilots complain they had experienced unusual turbulence as they flew near wind farms.

Kansas is one of the leading states for wind farm developments; there are 16 wind farms in Kansas, with proposals for 58 more.