When the call to battle sounded in April 1917, the Navy air arm could muster at its one air station only 48 officers and 239 enlisted men with some experience in aviation, and 54 aircraft none of which was fit for patrol service. The problems of building this small force into an effective fighting unit were enormous. Yet, when the Armistice was signed 19 months later, there were 43 air stations in operation at home and abroad, an aircraft factory in production, and numerous schools, assembly plants, repair depots and other facilities providing the needed logistic support. Aviation personnel numbered over 39,000, a figure nearly equal to the total in the entire Navy at the start of the war. http://www.history.navy.mil/branches/ww1av.htm
Perhaps it's worth noting that the above post refers to US Naval aviation. This may not be obvious to some who are new to the subject. The definitive book on the subject is R D Layman's Naval Aviation and the First World War; its impact and influence, ISBN 1 55750 617 5. Gareth
