gunsight's aim-point to take this into account, with the aim point presented through a reflector sight. The only manual "input" to the sight was the target distance, which was typically handled by dialing in the size of the target's wing span at some known range. Small radar units were added in the post-war period to automate even this input, but it was some time before they were fast enough to make the pilots completely happy with them. The first implementation of a centralized fire control system in a production aircraft was on the B-29. Post-World War II systems By the start of the Vietnam War, a new computerized bombing predictor, called the Low Altitude Bombing System (LABS), began to be integrated into the systems of aircraft equipped to carry nuclear armaments. This new bomb computer was revolutionary in that the release command for the bomb was given by the computer, not the pilot; the pilot designated the target using the radar or other targeting system, then "consented" to release the weapon, and the computer then did so at a calculated "release point" some seconds later. This is very different from previous systems, which, though they had also become computerized, still calculated an "impact point" showing where the bomb would fall if the bomb were released at that moment. The key advantage is that the weapon can be released accurately even when the plane is maneuvering. Most bombsights until this time required that the plane maintain a constant attitude (usually level), though dive-bombing sights were also common. The LABS system was originally designed to facilitate a tactic called toss bombing, to allow the aircraft to remain out of range of a weapon's blast radius. The principle of calculating the release point, however, was eventually integrated into the fire control computers of later bombers and strike aircraft, allowing level, dive and toss bombing. In addition, as the fire control computer became integrated with ordnance systems, the computer can take the flight characteristics of the weapon to be launched into account. Land based fire control Anti-aircraft based fire control By the start of World War II, aircraft altitude performance had increased so much that anti-aircraft guns had similar predictive problems, and were increasingly equipped with fire-control computers. The main difference between these systems and the ones on ships was size and speed. The early versions of the High Angle Control System, or HACS,