A Defense Department study published recently said that under the right circumstances windmill farms used to generate electricity have the potential to degrade the tracking capabilities of ATC radar. The study doesn’t cite any examples of this happening outside of flight tests done in the UK but recommends that more studies be conducted. According to an FAA spokeswoman, the agency is continuing to review all applications for wind farms it receives, the number of which has increased dramatically over the last several years. However, she said the FAA has completely denied only four permit applications since 2004 due to possible radar interference.