The distinction between drones and guided missiles is a bit arbitrary, as either can be remotely piloted or steered by an internal guidance system. In fact, both categories have a common ancestor. Designed in WWI and dubbed an aerial torpedo, the Kettering Bug was a minature biplane carrying explosives. With a rudimentary, pre-programmed guidance system, the Bug would fly a set distance (up to 75 miles, and counted out by an odometer attached to the propeller), and then crash to the ground, hopefully hitting its intended target. Developed too late to be used in the war, the concept was tested further during the interwar era; the UK's ship-launched RAE Larynx was an early example. While the Bug and the Larynx were never used in war, drone-like flying bombs have seen a recent revival, notably with America's Switchblade piloted missile.