I'm not sure you really can, as far as I'm aware. You could just set all of their health variables to 9999 or something, making them virtually invincible, but I don't know of a method of disabling vehicle/ plane damage entirely. I wouldn't recommend doing that though. Just tell your players to be careful while driving/ flying and learn how to handle their vehicles better. On my server, we use a mod called Progression and another mod called Custom NPCs and force players to go through driving a flying tests to prove they deserve the privilege of using those things. You may want to consider something like that.