FWIW, I avoid airplanes, diving when they're spotted..
- My sub is a relatively large, slow and easy target for them, while they are at best a challenge for me to hit.
- I may be paranoid, but it seems the game AI directs the A/C to radio my position to IJN HQ and soon I have more company than I want. Don't see an upside to giving them the opportunity
The only thing I use the AA for is sinking sampans and fishing boats with the 40mm Bofors being very effective for the task.