NEWS FLASH
Air Serbia and Turkey's Atlasglobal have further expanded their codeshare partnership. The Serbian carrier has now placed its "JU" designator code and flight numbers onto Atlasglobal's services from Istanbul to Antalya, Izmir, Bodrum and Gaziantep in Turkey, as well as Tehran, Kuwait City and Tel Aviv. On the other hand, the Turkish carrier now codeshares on Air Serbia's flights from Belgrade to Tirana, Skopje, Prague, Sarajevo and Vienna, whilst retaining rights to sell marketing flights to Podgorica and Tivat. Atlasglobal will boost its operations between Istanbul and Belgrade to daily flights next summer season.

Comments
Connecting flights are very often cheaper than direct flights so if the price is acceptable there might be for example IST-BEG-TIA.
Few days ago I found that in summer it is the cheapest to fly from FRA to BEG via TGD with YM
https://www.exyuaviation.com/2018/07/serbian-regulator-blocks-turkish.html
An elephant never forgets..