The 4th and final variant of the F4B was the -4 that first flew in July 1931. Of the 92 that were built 21 were assigned to the USMC. The F4B/P-12 was the last wooden-winged, biplane fighter that Boeing produced and used by the U.S. Military. The large purchase of 586 aircraft of all variants was partly to help Boeing survive the Great Depression and establish it as a major aircraft manufacturer. VF-6 served on board the USS Saratoga from 1932 – 1936.