I concur, an Ada Maru... Now, they were not zigging at all though, correct? Had you sunk a ship in the area earlier? I ask, because in theory (theory), the planes don't spawn without having a reason, though there are "patrols" supposedly. The one when you are targeting the DD, that would make sense that you might have an airplane coming...
What I'm going to do is build an IJN airplane line-up mission - have I done this before (deja vu)? Anyway, if that doesn't work, then I'll put a couple of sampans off the coast by an airplane base, and see if I can get a CTD that way. Thanks for the vidz Immelmann, very helpful!