Do the planes use some 'magic' ?

[XenonSurf]

Hi,
I'm a few hours in the game going through the tutorial missions.

My first impression of the game...
...is a good one, especially the presentation, manual and in-game tutorial is really helpful. I appreciate the indepth historical context too. What I miss are some dedicated screens at least for TMA and navigation, the player should think he is in a real boat and not in some kind of movie, maybe some 2D/3D walkaround in the boat would largely increase the game immersion. The realtime outside 3D view is of course awesome but very unrealistic, real skippers would give their right legs to have such a view in combat...But then: Fortunately undetected things are not shown, good thing.
Well done Killerfish Games

On to my title subject:
In the torpedo tutorial, I had the idea to make use of the radar on the surface to attract the plane flying around and see how it reacts. Soon he came finding me, and I was not successful in evading his droped torpedo which damaged my hull down to 31% and a complete flooding in the propulsion room. I was able to contain the flooding and evade and here comes the 'strange and magic' part of the hunt: I changed course and depth several times, however the plane was at some point always flying over me and I could see blinking sonobuoys very near to my real position. But no more torpedos droped, was he out of stock after only 1 drop? That would be a game bug I think.
Unless I misunderstand these blinking buoys. I find it strange that whatever I do, whatever course underwater I take, at some point the plane 'magically' overflies my exact position and a blinking marker appears nearby. Is this normal, what's up with this ??

Thanks to feedback, cheers,