Twice in the 70s I have been on a crew tasked to transit Turkish airspace heading for points east, once on a much looked forward to FEAF ranger to Singapore. On those occasions we got no further than Akrotiri because our NATO ally had refused diplomatic clearance to cross their airspace. What with that, and frequent French ATC strikes, I often used to wonder how our Soviet opposite numbers must have chuckled - can you imagine them asking for diplomatic clearance to overfly Poland, for example?