What was the main use for airplanes in World War l?

What was the main use for airplanes in World War I? Airplanes enabled soldiers to observe troop movements and locations. Airplanes allowed for the quick movement of resources. Airplanes eliminated the need for soldiers in the trenches.

Explanation: In my words i think because if they need to shoot from high ground insted of from the floor so they can get a better shot.

answer placeholder because the system is messed up