Deptrai...i've read your article with much attention, but respectfully i humble think you are a lil' ''outdated'' regarding examples given.
There is no such airline named "Air Mongolia", and both KD Avia and Union(Kras) stopped flying many years ago.
Regarding the convenience Reg. Countries,
AFAIK there is only one or 2 bizjets registered in San Marino, and about Liberia since the good old pair of L1011 freighters on the new prefix=A8 (after historic EL), not a single plane got any Liberian registration....these L1011 refers to the last flights made around big Asian Tsunami some years ago...iirc, just my 2 cents.