The high frequency of the air attacks is to make the game more 'exciting', presumably as part of the efforts to widen the sim's appeal (no bad thing in itself), but they've overdone it a bit for most people however.
There are some mods available (check the modder's forum) which will tone things down a bit if you find it annoying. Nevertheless, despite the somewhat unnerring accuracy with which aircraft seem to vector to your position, the Japanese were not totally incompetent in these areas and did have plenty of maritime patrol aircraft, so it's not desperately wrong if you are near the Japanese coastline or territories they have held for some time.
You can actually mod stuff like that yourself fairly easily to suit your preferences, as it's just a line or two in the config files that determines things like that.
Chock
