When we went in January, all flights were diverted to Thessaloniki in Greece, although we were supposed to go to Sofia there were people in the airport who were supposed to fly to Plovdiv.
we came back on the tomson flight on Saturday. Just before the inward flight was landing the fog dropped, the plane circled for about 20mins but no good, then it got diverted to sofia. We had to collect our bags and coach it to sofia. It was a pain to be honest, yet the staff were fantasic and there was no messing when we got to sofia. Planes can take off ok in the fog but not land because of their outdated systems.
Conditions are fantastic so worth the hassel