I can’t seem to find a way to change the exit vehicle key from “F” to anything else, occasionally I get a bit slopy and accidently hit the 'F" key when I am flying and before I can stop it, it happens almost instantaneously, and I find myself free falling.
Am I missing something is there a way to remap this command ?
The same thing happened to me yesterday
I have not tried it yet, but next time I play, I’m gonna try to change it to CTRL-F so I don’t “fall out” of my plane in the event my fat fingers press F instead of D. Which of course has happened to me on multiple occasions. SMH. 
EDIT: I checked the options and it seems you can not change it. Bummer… 
I tried to do that today but for the life of me I couldn’t figure out a way to make it happen because it doesn’t appear that it’s something you can change but maybe I missed something?
Sadly we still cannot change the key for exiting a vehicle.
I also have exited by mistake…
More than 1-in-5 people suffer premature ejection from vehicles.
Consult your developer today.