Was there an "ideological" selection process?
Or something that the first years or so you would only be allowed on domestic flights (e.g. Moscow-Kiev), and maybe later on flights to other "socialist fraternal countries" (Moscow-Berlin), and if you were lucky, then on flights to the West, like Moscow-Paris?
Would it have been possible to defect on an "international" flight? When there was the old trick of "holding your family hostage in USSR", could you have gotten the job in the first place if you were single?
To add onto this, what was flight service like in the USSR as compared to Western service at the time, and how common was commercial flight? Who was flying on these planes?