We are going on the Rick Steves Greece tour in June then on to a wine tour of the Adriatic that starts in Belgrade. I am looking for flights from Athens to Belgrade. Air Serbia is listed but doesn't have the best reputation as far as I can tell. Anyone have information regarding this leg of our trip?
Aegean also flies between Athens and Belgrade.
Skyscanner.com is a good source of schedules for intra-European flights. I don't think you'll find a lot of options for that route, but on the random day I chose in June, there was a non-stop flight on Aegean Airlines as well as the Air Serbia option. I don't know whether there are other airlines flying between the two cities.
Looking at skyscanner, there does seem to be differences in available flights, depending on which day of the week it is.
I see the tours end on Wed, Fri or Sun.
You should plug in your date to see what choices there are.