Zeros would not be flying at night excet as erzatz night fighters right over a target area. None of the CV planes should be seen at night at all, frankly. Flyingboats maybe. In terms of them making a bee-line for the player, seems like that is the way they model such air encounters. the planes that are not coming towards you you never see (they're not really there, but you get the idea).
Since the in game visibility range is so short (it's 8km, right?) I'd just assume they spotted you from farther away than 8km. Not sure, but a surfaces sub might be not to hard to spot with a phosphorescent wake...
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