William Carl Diehl (1891-1974) was an aviation pioneer and a member of the Early Birds organization. In 1914 he built and flew a monoplane and in 1915 he helped establish two flying schools, an unsuccessful school in Chicago and a school on Long Island. During the time he was working at Long Island, he helped to organize the United Eastern Airplane Company which manufactured airplanes. During World War I, Diehl was a civilian instructor for the Army Air Corps. In the late 1910s and early 1920s, Diehl established a commercial flying taxi service, performed stunts for movie production and for Pathe News, and barnstormed around the nation. He began work in 1926 on patents for aircraft mufflers and values. Diehl worked during 1927-1930 at the Wright Aeronautical Corporation at Paterson, New Jersey as an engine flight test pilot. Diehl returned to his original occupation of plumbing but continued flying until 1945, and continued his patent work until the early 1970s.