In the early 1930s Boeing developed a series of biplanes designated the F4B for the US Navy and US Marine Corps but was a P-12 for the US Army Air Corps. The aircraft were first accepted in 1929 and served as the primary fighter. The P-12 was built in 6 successful variants while the F4B had 4. The P-12 was replaced by the Boeing P-26 in 1934-35 but the F4B carried on with operational duties until the Grumman F2F/F3F series completely replaced them in 1938.
Boeing built one Model 218 to test design features for the F4B-3 and P-12E aircraft. During testing it was designated an XP-925 registered as X66W c/n 1260. The US Army and Navy did testing of the aircraft using the registration NC66W. Robert Short was the pilot hired to help sell the X66W to China. In February 1932 while flying X66W Short engaged a Japanese flight of 3 bombers and 3 fighters. Short managed to down 1 bomber before being mortally wounded and the loss of the only Model 218.