Is there a possibility to reset a flight after a crash to the last stable position? I checked possible key assignments but did not succeed.
Not as far as I know…but you can save a flight in midair (through the pause screen) and load it in again through save/load.
I often do this to practice difficult approaches.
You can also skip phases of a flight in case you have to start from the top. Quick access menu (the top menu) > Travel To > and just choose to skip to take off, cruise, approach, or final.
Could you elaborate - how do you save an in-progress flight?
Pause the flight in midair, click on load/save, select ‘save’, a window will open and you just save the flight under some suitable title.
If you then load that flight at any time you will start in midair form the point at which you saved the flight.