[EJGr.Ost_Caspar]

Its mainly, what IceFire said. We have technical and - even more - legal restrictions. If we could handle these problems, I'd be very happy, but currently its out of our possibility.
What we need is a WW2-airwar-enthousiast, who is at the same time sound expert (means who can provide and work with legal samples - preferably recorded by himself).

EDIT: I recently bought a Medusa NX headset to work with my simple 5.1 onboard sound device, instead of my old stereo desktop speaker.
I was astonished, how nice the in game sounds are with this now! They are not only more intense on treble and bass, but I can also hear more different sounds.

I know, it is still not sounding like a true airplane, but you can do a lot already with such a low budged setup.