Why was the war in the air a significant battle of WWI? (Three reasons)

Question

Also, supporting evidence and examples would be helpful too.

Thank you
~Lucy

http://www.firstworldwar.com/features/aces.htm
http://www.firstworldwar.com/airwar/observation.htm

http://en.wikipedia.org/wiki/World_War_I#Technology

Fixed-wing aircraft were first used militarily during the First World War. Initial uses consisted of reconnaissance and ground attack. To shoot down enemy planes, anti-aircraft machine guns were used, and, more effectively, fast fighter aircraft. Strategic bombing aircraft were created principally by the Germans and British, though the former used Zeppelins to this end as well.

Towards the end of the war, aircraft carriers were used in combat for the first time, with HMS Furious launching Sopwith Camels in a raid against the Zepplin hangars at Tondern in 1918.