In the 90s I was a regular commuter between Hong Kong/Singapore/various others in Asia to London.
The routings often changed according to the geopolitical situation down below. Once, Chinese ATC refused to give a CX flight I was on from Honkers permission to overfly. No reason given, they were just being bolshie.
Another place that caused trouble once was the FRY while Nato were bombing the !!!!e out of the place. That was given a very wide berth!