 This point was reinforced after the loss of two Republic F-105 Thunderchief aircraft to obsolete MiG-17s on 4 April 1965.In April 1965, Harold Brown, at that time director of the Department of Defense Research and Engineering, stated the favored position was to consider the F-5 and begin studies of an "F-X".These early studies envisioned a production run of 800 to 1,000 aircraft and stressed maneuverability over speed; it also stated that the aircraft would not be considered without some level of ground-attack capability.