The wartime advanced American P-51 Mustang had six machine guns, with the most advanced version the P-51H with an 1,800 mile range, service ceiling 40,000 feet, and maximum level top speed of 487 miles per hour.
The US Army asked North American Aviation for a replacement of the P-40. This was the P-51 Mustang, with an Allison engine. Late models had a streamlined "bubble" canopy. By war's end the U.S. Army Air Forces had received 5,541 Mustangs.
The Royal Air Force of England also ordered the American P-51 but with a Rolls-Royce engine rather than the Allison engine. The first British order was late in 1942. As a result some late American orders also specified the Rolls-Royce, rather than the Allison engine.
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