development of the F.B.5, the Vickers F.B.9, had a more streamlined nacelle and an improved ring mounting (either Vickers or Scarff) for the Lewis gun. Fifty were delivered to Royal Flying Corps training units. A few served in some F.E.2b squadrons while they were waiting for their new aircraft between late 1915 and early 1916. Operational history The first F.B.5 was delivered to No. 6 Squadron of the Royal Flying Corps (RFC) at Netheravon in November 1914. On 25 December the first use of the F.B.5 in action took place, when F.B.5 No. 664 took off from Joyce Green airfield to engage a German Taube monoplane, hitting the Taube (and possibly causing its loss) with incendiary bullets from a carbine after the Lewis gun jammed. Eighteen days later, the same flight crew, Second Lieutenants M. R. Chidson and D. C. W. Sanders, flying the first F.B.5 in France, No. 1621, were forced to land behind German lines, and the new plane fell into enemy hands. The F.B.5 began to be seen on the Western Front when the first reached No.2 Squadron RFC on 5 February 1915. The type served in ones and twos with several other units before No. 11 Squadron RFC became the world's first fighter squadron when, fully equipped with the F.B.5, it deployed to Villers-Bretonneux, France on 25 July 1915. Second Lieutenant G.S.M. Insall of 11 Squadron won the Victoria Cross for an action on 7 November 1915 in which he destroyed a German aircraft while flying a Gunbus. No. 18 Squadron RFC, which deployed to France in November 1915, also operated the F.B.5 exclusively. Early aircraft were fitted with British-built Monosoupapes, which proved less reliable than French-built engines, while much work was done before a useful gun mounting became available. Although its forward-firing machine gun was a great advantage, the fighter did not have the speed or rate of climb to pursue its quarry; thus, the F.B.5's performance proved to be inadequate for its intended role. This can be illustrated by noting that only the single pilot/observer team of Lionel Rees and James McKinley Hargreaves became aces while flying this type. By the end of 1915, the aircraft was outclassed by the Fokker Eindecker. Examples of the improved Vickers F.B.9 were sent to France, pending sufficient supplies of the Royal Aircraft Factory F.E.2b, but the active career of the Gunbus was soon over. The remaining examples