The great-circle route from Western Europe to, say, Japan involves putting in a lot of miles above Russia, for example like this (London Heathrow–Tokyo Narita; map from gcmap.com).
Would routes like that have been possible during the days of the Soviet Union or would civilian planes have had to take a more circuitous route, flying south of the USSR and maybe even avoiding the Warsaw Pact countries, too?
I'm aware that at least some of Soviet airspace was prohibited which, for example, led to the Soviet Air Force shooting down Korean Air Lines flight 007. Presumably, the route shown in the map would be prohibited, since it goes over the Kola Peninsula, where the Northern Fleet is based and Novaya Zemlya, a major nuclear weapons test site.