Hi wiedehopf,
Some interesting ideas there. I've wondered if they shortened it to 'BH' although even then, I'm pretty sure there wasn't an [ i ] sound in the first syllable. Burgas is pronounced with a [ s ], not a [
ʃ ] (or so Wikipedia tells me
)
As you say, I guess that unless we can find any BH Air pilots on here (or any controllers?), it's anyone's guess...
j'sd