As released, this requirement specified a top speed of Mach speed 1.4 to 1.5; however, during 1956, the specified speed was revised upwards to Mach 1.7-1.8.
No momento de ser publicado o requerimento especificaba unha velocidade máxima de Mach 1,4 a 1,5; porén, durante 1956, a velocidade revisouse e ampliouse ata Mach 1,7-1,8.