Question Creating a seamless terrain for a simple aircraft game

Hi.

I'm trying to make a simple aircraft game, in which the player can shoot missiles at the enemy craft and the enemy craft can shoot missiles at a random rate at the player. I'm half done creating it, now I need to learn how to create a seamless terrain under the crafts, so that when they move, the ground seemingly remains forever. This terrain can be a simple mesh -- cuz I don't need a detailed 3D terrain at this point. But I may consider adding a 3D terrain afterwards. Could you guys please briefly explain or point me to a tutorial that explains how to make a seamless terrain (with C#)?

This is a short clip that demonstrates the current development state. As you can see, I need a terrain below:

Thank you very much!

 

I believe these 3 videos from Brackeys can help you a lot:

MESH GENERATION in Unity - Basics
PROCEDURAL TERRAIN in Unity! - Mesh Generation
MESH COLOR in Unity - Terrain Generation

 

Thank you!