(old usage) a pilot of an aeroplane, especially a war plane;
a person who flies an aircraft, especially in the early days of flying aircraft,
An aviator was a fighter pilot who fought from an aircraft — air-to-air combat, i.e. shooting enemy fighter planes in the air, or dropping bombs on chosen places in the enemy country.
James Stewart was known to be the best aviator at Tibenham, a World War II Royal Air Force Station near England.