The Model 15 (PW-9) was the first successful Boeing-designed fighter and established the company as a major American builder of military aircraft.
Its internal bracing was arc-welded tubing rather than the spruce and wire used in older biplanes. However, it still had wooden spars and ribs. It was designated PW-9 (for “pursuit water-cooled design 9”) by the U.S. Army and designated FB-1 by the Navy.
Between 1923 and 1928, Boeing built 157 PW-9/FBs in different versions, as well as 77 derivatives as NBs (Navy training planes). The NBs were 4 feet (1.21 meters) longer than the PW-9/FBs and powered by either 180- or 200-horsepower engines. Boeing also sold five NBs to Peru.