4. RAF Upper Heyford Base: England
During World War I, the RAF constructed the RAF Upper Heyford as an Air Force Station. That was in 1916, but they didn’t use it for flying until 1918. It remained a flight training facility after The Great War, lasting through the Second World War. Sometimes after that war ended, the United States took over the base as a strategic air command center for the U.S.A.F.