Thanks for your answer on my comment. Very kind of you indeed. Obviously the latest DLC or some newer patch connected to it did introduce the bug.Unfortunately I can't hide my infuration about the present state of naval air warfare concerning carrier planes. If I'm not very much mistaken this aspect of HOI IV did work fine and dandy not to long ago. I find it therefore hard to understand, why the solution for this problem has to wait until the next DLC is released. This is In my view not only inacceptable long because naval air combat worked just fine a few months ago, but also for the simple reason that this part of the game is of substantial importance.
AFAIK 1.4.2 still works without this bug but the land AI is dumber there so there's a tradeoff. Also in 1.4.2 there's no obligatory faction auto-join which is a pro for me but GUI scaling in 1.4.2 is worse so there's another tradeoff.