increased to over , or with a 90 gal drop tank. The first test of the aircraft was in intercepting V1 flying bombs and the Mk XIV was the most successful of all Spitfire marks in this role. When 150 octane fuel was introduced in mid-1944 the "boost" of the Griffon engine was able to be increased to +25 lbs (80.7"), allowing the top speed to be increased by about to at . The Mk XIV was used by the 2nd Tactical Air Force as their main high-altitude air superiority fighter in northern Europe with six squadrons operational by December 1944. One problem which did arise in service was localised skin wrinkling on the wings and fuselage at load attachment points; although Supermarine advised that the Mk XIVs had not been seriously weakened, nor were they on the point of failure, the RAF issued instructions in early 1945 that all F and FR Mk XIVs were to be refitted with clipped wings. Spitfire XIVs began to arrive in the South-East Asian Theatre in June 1945, too late to operate against the Japanese. Several Mk XIVs were rumoured to have been buried at an airfield in Burma after the war. FR Mk XIV Late in 1944 a number of high-back full-span Mk XIVes were converted by the Forward Repair Unit (FRU) to have a single camera fitted, facing to port or starboard; a conversion identical to that used on the FRU-converted FR Mk IXc. To achieve this a new hatch, similar to the radio hatch on the port side, was installed on the starboard side, and both hatches were fitted with camera ports in streamlined blisters. Otherwise this version of the FR Mk XIVe was essentially the same as the standard aircraft. These field-converted aircraft were allocated to 430 squadron RCAF. Later, purpose-built conversions, also known as the FR Mk XIVe, had the later cut-down rear fuselage with its tear drop–shaped canopy, port and/or starboard camera ports (without blisters), and an additional rear fuel tank of 34 gallons which extended the Spitfire's range to about on internal fuel. Because it was used mainly at low altitudes the "production" FR Mk XIVe had clipped wingtips. In total, 957 Mk XIVs were built, over 430 of which were FR Mk XIVs. After the war, second hand Mk XIVs were exported to a number of foreign air forces; 132 went to the Royal Belgian