I have this huge amount of planes from every campaign. I never play planes, so those are quite useless for me. I actually asked about this feature before, but i only heard that we will be able to sell squads.
Still in War Thunder you can sell unwanted vehicles too. Would really like to sell all those planes, so the grind doesn´t feel so bad, after the merge happens. Better to have silver, then having this in your library, knowing you have grinded for this unwanted stuff for hours, because of the old campaign system.