As a 'frequent flyer' on this route, my sympathy goes out to the BA crew and a strong dose of being thankful for my good luck (thus far) not to be on the receiving end of a 'close inspection'. One of the most insidious issues we have to face is the sectorisation that is invoked in many European FIRs. In the Bucharest FIR there is a frequency change about 40 miles from the Budapest FIR, least when you expect it (too soon for an ATC FIR handover, too soon to expect an inter FIR handover). Germany is another classic case in point, it seems that if you are heading E-W in Germany, you get a freq change every thirty miles (slight exaggeration I know, but the point is made). We can use various techniques to alert us to the passage from one FIR to anther, but we are blissfully unaware of how each FIR is divvied up into sectors.