Helicopters circling as they make continuous passes and attack targets behind the 1200 Area. During the evening, as darkness arrived, the helicopters would land, refuel, reload, and take off, upon departure they would turn off their running lights as they departed towards the 1200 area to continue their machine gun attacks on ground targets. Watching this for hours, I observed one helicopter pilot forget to turn off his lights and the tracers from the ground were very accurate in acquiring the helicopter when the pilot arrived over the target area. No other helicopter pilots forgot to turn off their running lights..