I'm remembering this from my distant memory, so I would welcome those who can correct me if I'm wrong on any details:
JAT flew 707's from Pula in 1985, in subsequent years operated by 727's of JAT. Technically the flights were Air Yugoslavia hense the JR rather than JU flight prefix. Those of us in the Cookridge/Horsforth area may remember the 707's performing on some occasions ILS's on 32 with the visual break from the outer marker onto 14 in the days before 14 had a glideslope. It made for some impressive flyovers of that part of the city.
Aviogenex operated Split with 737's on a Saturday evening but occasionally dropped a 727 in. Flightrider may remember a photo opportunity we both had on the apron for one of the latter.
Ljubljana was operated by JAT DC9's in 1985 on a Monday evening replaced by Adria (Tarom leased) Rombac 1-11's and DC9-30's in subsequent years on a Monday morning, normally on the ground at the same time as the Wardair 747's. If my memory serves me well LJU did not operate in 1986.
Dubrovnik was operated by JAT in its 1st year (1986) via Pula on a 727 on a Monday morning, in later years Adria direct on a Saturday evening, MD-80's predominantely and a number of A320's in the final year or so. If I remember well the first Adria A320 visit was the day that Leeds United won the (old) Division One title. One year (I forget which) they also used an MEA 707 on some occasions.
Yugotours being the charterer on all the above, and I'm seriously showing my age.
Back to the subject in question, I understand Balkan were looking at Pula from LBA in S09 if a suitable aircraft became avaliable, so I guess if the right people talk to each other then Balkan as a sharer on Dubrovnik may be a revised opportunity for both Jet2 and Balkan.