 Typical designs featured variable-sweep wings, weight over , included a top speed of Mach 2.7 and a thrust-to-weight ratio of 0.75.When the proposals were studied in July 1966, the aircraft were roughly the size and weight of the TFX F-111, and like that aircraft, were designs that could not be considered an air-superiority fighter.Through this period, studies of combat over Vietnam were producing worrying results.