Your program does NOT mention that when the MIG25 goes above 2.8 Mach or so, it can only stay at that speed for a few minutes before 1) the engines blow up and 2) it runs of fuel. Compared this to SR71, which can fly at Mach 3 for HOURS. So in terms of "catching the SR71" using the Foxbat, it would take an enormous amount of luck (be at the right place at the right time for an ambush). Given the SR71 was semi-stealthy (it was one of the first aircraft with stealth purposely designed and built in, including early radar-absorbing paint and canted vertical tail fins that you see in all 5th generation aircraft), it makes the job of intercepting an SR71 vastly more difficult for the Soviets. The fact that the SR71 served in the USAF for 30 years with hundreds if not thousands of missiles and all kinds of aircraft chasing it without being hit tells you how tough it is to get close to a plane like that.