Enemy pilots started throwing grenades, grappling hooks, and shooting each other with almost no chance to hit anything until the mounted machine gun came into effect.
Planes were used by both sides to drop bombs on eachother. The planes were quite slow and only able to hold small bombs. Fighter aircraft were used to protect the slow moving bombers and to attack any enemy aircraft.
Aircrafts were originally used for reconnaissance, where pilots would scout above the battle and figure out the movement of their enemies.
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Zeppelins and smaller airships were mostly used for reconnaissance by France, Italy, and Germany but were also used for naval battles.
Long range overwater reconnaissance and anti-submarine aircraft, shorter range floatplane reconnaissance and fighter aircraft, and ship borne aircraft were three major naval aircrafts used during WW1.
Pilots would contact allies to readjust artillery fire with just transmitters but that soon changed to light two way communication radios.