Henry Harley "Hap" Arnold (June 25, 1886 – January 15, 1950) was an American general officer holding the grades of General of the Army and later General of the Air Force. Arnold was an aviation pioneer, Chief of the Air Corps (1938–1941), Commanding General of the U.S. Army Air Forces during World War II, the only Air Force general to hold five-star rank, and the only person to hold a five-star rank in two different U.S. military services. Arnold was also the founder of Project RAND, which evolved into one of the world's largest non-profit global policy think tanks, the RAND Corporation, and one of the founders of Pan American World Airways.