what is the best way to to an insanely large map

for the last month or so i have been doing an air combat game and one of the problems i have ran into is the fact that the default terrain for unity is to small when seen from the air with air vehicles. my question to you guys is what approach would you use for a pretty large map (at least 10x the default unity size of 2000 x 2000) i have thought of having several of these terrains together, or maybe doing it in blender and importing it. also is it better to do chunks or one large mesh for the entire map? thank you all.

yea you just use chunking.

you have a dictionary of terrains and use it to look up nearby chunks and load them as needed.

the best way to implement this solution is to go on the asset store and buy an infinite terrain tool.

I would actually minimize the planes.

If you want to make maps just make the plane very small, and the terrain fairly big, change the tiling on textures and tweak some terrain settings,
Terrain Height/Width/Length.
Detail Resolution
Etc.

This way you can still have a smaller terrain that seems large because of the planes size.

Hope this helps!