The end of the Cold War has enabled aircraft to begin using a set of four polar routes. . . . "We anticipate that using polar routes will save passengers significant flying time. Airlines will use less fuel
and that will mean significant savings on each flight.”... [For example,] airlines traveling from
Toronto to Beijing will travel ...3,013 nautical miles through Russian and Chinese airspace.
"End of Cold War Opens Polar Routes," SpaceDaily, October 2000

Why would the end of the Cold War—or the Soviet system open up Russian air space?