I went on a orginazed tour of Belgrade in 1989. Superb museum if in a bit of a strange building. Lots off WW2 stuff(Spit,Hurricane,Me109 etc), some nice commercial stuff outside. JU52,Li2,DC3,Caravelle,Dove,Convair,IL14 and a Short Sealand.
We had a tour of JAT maintiance and the light aircraft. There were a couple of airforce YAK 40’s, most of the JAT fleet including ATR’s, all the DC10’s and the light stuf, Cessna 402’s,Agcats and AN2’s!
We didn’t see too much foreign visitors but did manage one of my only 2 Interflug 134’s( I saw them all after the fall of the wall at SCO).
We also did Zagreb managing to get detained by the authorities( a whole coatch of us!) for a hour. Somehow we kept braking down on the motorway opposite the Yougoslav AF AN26 ramp.