The spawned objects have bigger collider which dissables itself when player gets near and destroys object if it collides with another one spawned. For the planes there are small planes generated nearby you to walk on and one bigger that is slightly underneath the small ones so you can see terrain in distance. The bigger one moves with you but the small ones get destroyed behind you and generate in front of you. I used shader so you can not see the differences in textures. I hope this will help you.