Also tracked down cited reference and even interviewed personnel involved (more on this if necessary).  The aforementioned article, while interesting with respect to the MiG-31's technology and capability, does not consider the fact that the USA and USSR were right in the middle of Gorbachev's "Perestroika", arms reduction treaties, and other positive diplomacy.  Above all else, the SR-71 is a diplomatic tool that is to be used delicately.  The flights became more and more conscientious of the fact that relations between the USA and USSR were softening and warming.  It had nothing to do with so-called intercepts.  The physics of such an intercept is a whole other argument.   jason.r.newell