Istanbul might not be an awful shout tbh, though if I was wanted internationally and I'd successfully entered somewhere Montenegro I'd probably sit tight for a while. It's a small country, but it's quite nice and you could probably fly under the radar for a while if you kept your nose clean.

> There are fine destinations: Belgrade, Istanbul, Vienna, Manchester, Varna (Bulgaria).

I assume these are the commercial destinations. Is it out of the question that he chartered a flight?