State government inspectors have been using aerial surveillance to watch coal operators in central Appalachia.

Helicopter flights have cost The Kentucky Division of Mine Reclamation and Enforcement more than $477,000 over the past four years, according to documents obtained by The Associated Press.

News of the flyovers surprised mining industry leaders, including Kentucky Coal Association President Bill Bissett, who protested the covert nature of the inspections and questioned their effectiveness.

Kentucky Department of Aviation documents released to the AP under an open records request show that state police and wildlife officers are also using planes and helicopters for aerial surveillance.