Oh. I knew for the letters but not for the tail number, that is really good to know. Thank you for the precision Jojo.
But as you say the beginning of the registration needs to be on the skin itself, and we don't have it (for the 115-K_,115-Y_) unless we do a custom one which won't be visible in multiplayer. But yeah, it may be just me who am too picky on little details :D.