Thanks ORAC and IGh,
I had better explain why I am interested in this.
I am long retired and amuse myself these days writing fictional short stories on airline themes. The one I am working on at the moment is set in 1966. A 707 is on it way at night eastbound over Turkey towards Teheran. For various reasons the crew make a major navigational error - they don't turn south towards Tabriz after passing Van but continue straight on into Soviet airspace out over the Caspian Sea south of Baku.
They are seen by Russian military radar and two MIG 21s are sent up to intercept. Fortunately the 707 crew realise their mistake, turn south and cross into Iranian airspace before they can be intercepted. They remain totally unaware of the MIGs or what might have happened.
In 1966, Turkish civil ATC did not have radar coverage in this area, they used procedural control. 1966 is not long after the US had removed the Jupiter missiles as part of the agreement which ended the Cuban Missile Crisis but, presumably, there would still be a military presence of some sort and military radar coverage - either US or Turkish. In my story they do not observe the 707 entering Soviet airspace.
The first the western allies know about this navigational error is when the Russians accuse the UK of mounting a spying mission and use this to embarrass the western negotiators so as to extract some concessions during the nuclear non-proliferation talks which were taking place at that time in Geneva. The UK Foreign Office then summon the chairman of the airline who instigates an internal inquiry. The action in my story takes place mainly in the flight manager's office when the captain is interviewed.
So, you see, all I need to know is; is it plausible, for whatever reason, for the Turkish military (or the US if they were still there) not to notice the 707 straying into Soviet airspace?
The story is prompted by a real incident!!