I dunno, a viable submarine aircraft carrier might be too technically complex and too expensive for too little practical utility in a contemporary threat scenario, it would be a hard one to realistically justify I think. Although, I think there would be a lot of mileage in submarine launched flying drones. Something small that could be fired from the torpedo tubes maybe(?).
But, an attack submarine that could also fly, now that would be something!
I seem to remember an ancient American TV series (black and white I think, maybe from the 60s???) that featured a US Navy(?) flying submarine, it used to be repeated in a kid's TV slot on Sunday afternoon British TV when I was very young back in the very early 90s (alongside such gems like the original 'Lost in Space'), can anyone remember the name of the show? I think one of the main characters was called Kowalski, and it was sort of similar to the original Star Trek but with an overdose of Cold War paranoia.... Oh, and the submarine had these huge distinctive windows - an observation deck - maybe in the bow I think, that the crew could peer out of and use to enjoy the under sea sights(!)... was pretty crazy, but it was one of my favourite shows at the time, although I can barely remember it now!