While not part of the present Army Aviation Branch's heritage, United States military aviation began in 1907 with the Signal Corps Aeronautical Division and its acquisition of its first heavier-than-air aircraft, an airplane built to Army specifications by the Wright brothers. During World War I, the Air Service's aircraft strength grew from a few dozen to more than 11,000 planes, and the number of aviation personnel came to total more than 190,000. The Army Air Service was created with the disestablishment of the Signal Corps Aviation Section in May 1918. After World War I, General William Mitchell and other Air Service leaders spoke out forcefully in favor of an independent air force. Since they envisioned aviation as a separate striking force, capable of independent operations, they opposed its remaining a supporting arm of the ground forces. Although Congress, as well as most Army leaders, rejected Mitchell's argument, the Air Service did become a separate combat arm, equal in status to the infantry, cavalry, and artillery. In 1926, the name of the air arm was changed to Army Air Corps, and then, in June 1941, the Air Corps and other Army air elements were merged to form the Army Air Forces, co-equal with the Army Ground Forces and the Army Service Forces.