I have flown Balkan, back in 1989, when I was only 9 years old.
I remember vivdly that their planes were remarkably clean and they did not have that fuel smell, which was a bit unsusual for me - as I was used to that aviation smell on Aeroflot planes.
I flew Balkan's Tu-154B (I think...) and Tu-134A-3. Both on one day:
Varna - Sofia
Sofia - Varna.
Sofia's airport - well, nothing special. Nice one. Quite big as well... In general, I liked Sofia.
I know, it's been ten years since I was there and lots of changes must've taken place. I'm sure the changes to the better...
Scotland - Russia