The first to be used operationally was the Aeronca GB-1, essentially an autopilot attached to a small glider airframe carrying a bomb. It was intended to allow the 8th Air Force bombers to drop their payloads far from their targets and thus avoid having to overfly the most concentrated areas of anti-aircraft artillery fire. It was first used on 28 May 1944 against the Eifeltor marshalling yard in Cologne, but only 42 of 113 bombs released reached anywhere near the target; most "spun in and exploded 15 miles from the target... many of the batteries failed to hold [their] charge").