As a witness to the removal of fallen U.S. troops from Afghanistan, Army Chaplain Christopher John Antal can't recall a time when that solemn ceremony wasn't conducted without the presence of drones passing along the horizon. They were sleek and quiet, making a gentle humming noise as they flew over the flight lines - where aircraft can be parked and serviced - of the Kandahar airfield in Afghanistan, where he was stationed in 2012.