Knew a guy from a former life who went to Russia regularly for business.
He told me there was a time when they couldn't get the second engine on a two engine plane started. They announced there would be a brief delay and to stay seated with seat-belts fastened.
Oh, goody, he thought. They are going to get us a replacement plane. But instead, another team arrived and tried to start the second engine.
They couldn't do it either, so the plane took off on one engine. Lucky for him, it landed safely at the destination.
There are several airlines that flew into the USSR but they had to fly to Moscow only. From there everyone had to fly Aeroflot. Government monopoly. My sister and brother in law went to central Russia in March a couple of years ago. Had some interesting stories about their flights.