The Grid: Oklahoma's power grid faces 'incredible' challenges - Article Photos 1/9

This July 8, 2013 photo provided by FirstEnergy shows a helicopter aerial saw trimming trees along a FirstEnergy transmission corridor in Doylestown, Ohio. Electric utility tree-trimmers have made their mark on the picturesque hillside where branches coming into contact with high-power lines helped set off a chain-reaction blackout stretching to Canada and the East Coast and fried household appliances 10 years ago. But the sound of chain saws isn't welcome to tree lovers who now see open skies where tall trees once shaded the power lines and the neighborhood. - AP Photo/HO, FirstEnergy