I remember reading a book on Victor Belenko who defected to the west in a Mig 25 Foxbat. I recall him saying that if they were lucky enough to get in a stern chase on an SR71, both going flat out, even firing air to air missiles at the SR71 they could not tag it. The Mig 25 is no speed slouch in it's own right Mikoyan-Gurevich MiG-25 - Wikipedia, the free encyclopedia . I believe he also mentioned that the radar on the Mig 25 was powerful enough that if they radiated it on the ground it would kill wild life on/near the runway they were using to take off from. Interesting man and story.

Bob