P-51B Mustang airplane model. In September 1940, the Packard Motor Company of the U.S. began license production of the Merlin V-1650-1 engine in Detroit, Michigan. With a new supercharger drive, a new V-1650-3 was mated to the first P-51B. Both the U.S. and England started the Merlin engine modification idea almost simultaneously. 10 airframes were modified in the U.S. with the Merlin, ,and these became the basis for the most successful fighter series of the war.
Flying for the first time on 30 November 1942, the XP-51B was soon modified with a larger coolant radiator scoop, which actually increased its top speed by 50mph and gave it a higher ceiling by 10,000 ft. The addition of an 85-gallon ,fuel tank behind the seat increased the P-51B's already excellent range, and it could now escort the bombers all the way to the target and back. P-51B Mustangs began arriving in England in September 1943 with the first Mustangs going to the 3354th fighter group at Boxted, England, and ended the war with the most air to air victories. A total of 3788 P-51B's were produced.