When it comes to the British turn, Yugoslavia is an Ally, because of the German attack before, so the territory of Yugoslavia is friendly to the British.
So in NCM the British fighters may land there.
Thank you! Before this thread, this effect had never really occurred to me, and I think I may have let a British plane or two sink into the Adriatic when it could have landed in Yugoslavia. Not that it would really have survived there anyway, but it’s always good to make life a bit harder for Italy when taking it.