The 278th Aero Squadron was a Air Service, United States Army unit that fought on the Western Front during World War I. The squadron was assigned as a Corps Observation Squadron, performing short-range, tactical reconnaissance over the VII Corps, United States First Army sector of the Western Front in France, providing battlefield intelligence. After the 1918 Armistice with Germany, the squadron was assigned to the United States Third Army as part of the Occupation of the Rhineland in Germany. It returned to the United States in June 1919 and was demobilzied.