And why have the individual aircraft codes , in black from "A" to "Z" started to disappear from the aircraft ?
Some of the airframes never had them in the first place. What has happened since the letters were first applied is that when the airframe is repainted (or has a repair done to that part of the tail) the letter is removed, but it appears to be outwith the contract to replace it! All airframes which pass through Valley have the letters reapplied where necessary thanks to some very helpful people in Station Graphics, but this may not be possible elsewhere. Or maybe noone cares!