The Organization of the Air Service of the American Expeditionary Force on November 11, 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 November 9, 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 i