Second Lieutenant William Thomas Barnes DFC was an English flying ace of World War I. He served as an observer/gunner in Bristol F.2 Fighters, gaining, in conjunction with his pilots, nine confirmed aerial victories (6 destroyed, 3 'out of control') over German Fokker D.VII fighter planes. William Thomas Barnes began his military service in the Royal Fusiliers; he had become a sergeant before he was commissioned a second lieutenant within the regiment on 10 June 1917.