The Soviets could shoot down an SR-71 that invaded their airspace by 1980 (I can't find a reference ; it seems likely we could shoot down a Concorde if needed. (I say likely rather than definitely, since a large part of the USSR deterrence involved scrambling interceptors before the SR-71 reached their airspace, and by 9/11 we no longer had a plane capable of launching an AIM-54 which could almost trivially shoot down a Concorde).
They did shoot down a U2; a Mig(31?) was able to gain missile lock on an SR-71. In any event shortly after they had developed the capability we ceased to enter soviet airspace with an sr-71.
