Hall Aluminum Aircraft Co. was formed 1927 to build all-metal aircraft for US Navy. Designer Charles Ward Hall produced metal wings for Curtiss HS-2L, prototype 2-seat Air Yacht and then important XPH-1 flying-boat based on Naval Aircraft Factory PN-11 (in turn based on British F.5). PH-1, -2 and -3 produced until 1940. Other prototypes were XFH-1 biplane shipboard fighter (1929), XP2H 4-engined biplane flying-boat (1931) and XPTBH heavy torpedo-bomber seaplane (1936).