Organization of the Air Service of the American Expeditionary Force

World War I Air Service recruiting poster, 1918
Active	3 September 1917 - 1919
Country	United States
Branch	United States Army Air Service
Part of	American Expeditionary Forces
Commanders
Chief of Air Service, American Expeditionary Forces, 3 September 1917	William L. Kenly
Chief of Air Service, American Expeditionary Forces, 27 November 1917	Benjamin Foulois
Chief of Air Service, American Expeditionary Forces, 19 May 1918	Mason Patrick
Insignia
Wing roundel of Air Service, United States Army aircraft

The Organization of the Air Service of the American Expeditionary Force on 11 November 1918, represents its maximum strength in World War I. Units of the Air Service are listed as assigned to the order of battle for that date, which was that of the Armistice with Germany. The first air unit arrived in France in September 1917, while the final air unit reaching the front did so on 9 November 1918. Unit operations began in April 1918. At the armistice, 57,508 officers and men served in the Air Service of the AEF, 24,512 in the Zone of Advance (combat area), and 32,996 in the Services of Supply (rear areas). Of its 6,861 officers, 4,088 were on flying status and 219 were qualified observation balloon aviators. 1,724 of those on flying status and approximately 100 of the balloonists served in combat units.^[1]

The First Army Air Service was activated 26 August 1918, with Col. Benjamin Foulois named chief over Col. Billy Mitchell. The Second Army Air Service was activated on 12 October with Col. Frank P. Lahm as chief, and the Third Army Air Service was created immediately after the armistice to provide aviation support to the army of occupation, primarily from veteran units transferred from the First Army Air Service.

The first two air combat groups formed in the AEF were the 1st Corps Observation Group, in April 1918, and the 1st Pursuit Group at Toul. Ultimately fourteen airplane and seven balloon groups were formed to support the operations of two field armies and five corps. The five pursuit and two bombardment groups were organized into two wings. The seven observation and seven balloon groups had one of each assigned to an army or corps air service. Two flexible "observation wings" were created to coordinate the reconnaissance activities of the five corps air services.

The basic units of the air service were the squadron for powered aircraft and the company for balloons. 45 squadrons (38 of which conducted combat operations) of aircraft and 17 companies of balloons served at the front. The 20 pursuit and seven bombardment squadrons were authorized 25 aircraft (including spares) and 18 crews each by the Field Service Regulations, while the 18 observation squadrons were each authorized 24 planes and 18 crews. Balloon companies were equipped with one balloon and approximately six observers each.