Thank you all for the replies. I'm going to try to change the config files (as suggested by oukej) although at first glance I haven't yet completely understood how that has to be done. I will go through the tutorial step by step and see if I can work it out.
As for the speed sensitive FOV I agree that especially in aircrafts it is pretty far away from what you'd experience in real life. Although I'm "only" flying small single engine airplanes and gliders, I would say that apart from being launched from a aircraft carriers catapult (or doing the poor man's version of it: a winch launch in a glider) or maybe sitting in a top notch fighter going from idle to full afterburner, you will probably never feel much horizontal acceleration or body movement in an airplane. If you do move, you've probably forgotten to properly strap yourself in - or you've just crashed ;-) But I guess in every game or simulation you have to replace some of the missing sensations (like haptic feedback) with things you can bring across a screen over to the player. An in this case the developers decided to use the FOV to simulate the feeling of being pressed into your seat while accelerating. Acceleration based character movement is much more realistic but only if it is a very subtle effect.