A wind turbine blade that absorbs radar signals has been demonstrated at a wind farm in eastern England.
Wind turbines confuse aviation radar signals, making aircraft in wind farms' vicinities difficult to track.
Defence firm Qinetiq and turbine manufacturing firm Vestas are developing "stealth turbines", with radar-absorbing materials and coatings.
The five-year effort may help many wind farm projects that are on hold because of so-called "radar clutter" concerns.
The project, part-funded by the UK's Department for Business, Innovation and Skills, saw a full-scale 44m prototype turbine blade fitted at a wind farm in Norfolk.
"The part of the turbine that gives you the greatest [radar clutter] problem is the blades, because they're rotating," said Mark Roberts, strategic business director for energy and environment at Qinetiq.
"We've got a coating for the fixed structure - the tower. We're hesitating from calling it paint, because it's actually quite thick.
"For the blades it will be material incorporated into the composite manufacture of the blade itself. In effect the whole of the turbine is made 'stealthy' but there's two solutions in there," he told BBC News.
The announcement follows Tuesday's pledge by energy and climate change secretary Ed Miliband of £5.15m to solve the problem of radar clutter.
The "stealth" blade's (left) radar signature is smaller than a normal one
The issue, he said, is currently holding up a total of more than 10 GW of wind farms in planning or development.
The new funding is to develop a system that works in an entirely different way.
The aim is to develop an application for radar systems that can detect wind turbines and subtract their effects from radar signals.
Mr Roberts concedes that the "stealth turbine" approach may help the issue, but cannot solve it.
"There is no single, silver bullet to this whole issue. Every proposed wind farm deployment is quite different in terms of number of turbines, location, proximity to radar and so on," he said.
"We can't say it will work in every circumstance but it will be a significant step in the right direction."