modate the new engine and a armament of four 0.50-in
machine-guns, a different designated was given depending on which factory had built the plane. P-51B's were planes built in Inglewood and P-51C's were built at Dallas.
P-51B and P-51C's began to enter operational service with the USAAF in Britain as part of the 8th Air Force. The 13th October 1943 saw this new Mustang complete it's first long-range escort
mission when a force of bombers were sent to attack the U-boat yard at Kiel. The P-51 Mustang, with the benefit of external fuel tanks, would provide regular escort for bombers of the 8th
Air Force, which included the Boeing B-17 Flying Fortress and Consolidated B-24 Liberator, during their perilous daylight operations deep into the heart of Germany. During March 1944 the
Mustang took part in it's first mission to Berlin and started being used operationally by both the 10th and 15th Air Force in Burma and Italy respectively. The RAF also started to
receive their lend-lease P-51B/P-51C's, designated Mustang III, around the same time and No.19 Squadron based at Ford, Sussex were the first to receive this new type, which would eventually
be used by at least 21 RAF squadrons, many of which were part of the 2nd Tactical Air Force. The RAF modified the original cockpit canopy which opened sideways to a sliding hood design to
overcome the poor rear view of the original canopy design.
Development of the Mustang continued and the next production version was the P-51D, with a modified rear fuselage, six 0.50-in machine-guns and a bubble canopy as standard, this was to
become the most produced version of the P-51. Later versions of the P-51D had a small dorsal fin added and racks to accommodate 5-in rocket projectiles. A change in propeller lead to a
change in designation to P-51K, and both of these planes were designated Mustang IV and MK IVA respectively by the RAF.
During 1944 as part of experiments into lightweight construction the USAAF had ordered three XP-51F's and two XP-51G's as part of this process. A new redesigned airframe was also produced
and as a result of an overview of the plane a new low drag section of wing replaced the laminar-flow design, the oil cooler was also replaced with a heat exchanger and the cockpit canopy
was stretched to reduce drag further. With a simpler structure and the removal of equipment no longer deemed necessary and the use of new lightweight materials being used a significant
reduction in the planes weight was achieved. Both prototypes were powered by different engines with a 1,695-hp Packard Merlin V-1650-7 engine powering the XP-51F and a 1,140-hp Rolls-Royce
Merlin 145m powering the XP-51G. Two P-51J prototypes of a similar design were ordered, however only one was finished and this would be powered by a Allison V-1710-119, 1,720-hp engine.
As a result of the prototypes the P-51H appeared powered by the V-1650-0 Packard Merlin, this was to be both the last production Mustang and the fastest with a top speed of 487 mph.
Further improvements had been made to the plane and as a result the plane was 40% lighter than the last Mustang in war time service the P-51D.
Another permutation of the P-51 was the P-82 Twin Mustang which was two aircraft merged together, however this didn't see service in World War 2.
A grand total of 14,819 Mustangs were built by the time production ended, seeing service with China, Netherlands and a few were also supplied to the American Volunteer Group (AVG) in China.
The end of the war didn't see the end of the Mustang as it remained in service with the US in some capacity until 1951, although under a different designation of F (fighter) - 51. In fact
the last Mustang was retired from the Dominican Air Force in 1984.