Unidentified pilot standing in front of U.S. Army airplane during World War I, 1918. The Air Service, United States Army, was a forerunner of the United States Air Force during and after World War I. In France, the Air Service of the American Expeditionary Force began combat operations in the spring of 1918. The Air Service destroyed 756 enemy aircraft and 76 balloons in combat. 17 balloon companies also operated at the front, making 1,642 combat ascensions. 289 airplanes and 48 balloons were lost in battle.