You know how on that snowy island, there is a small runway inside a mountain guarded by horrendously overpowered SAMs (surface to air missile)? Well there is a simple way to cheat that and peacefully enter the base!

Here is how to do it:
1- Choose a relatively small and maneuverable plane that you have already made
2- At the back of that plane, add a decoupler
3- on that decoupler, add a ton and a ton of tiny fuselage pieces. Make sure there are more fuselage pieces then parts of your plane
4- now start the game, decouple the decoupler that the pieces are attached to and find your way to the military base. You will see that you will not be detected! Now just fly peacefully in!

Here is one of my planes inside it