The P-51 Mustang was one of the most effective fighters of WWII. The first flight of the P-51 Mustang was in September 1942. The aerodynamics of the Mustang were excellent but initially it was underpowered. Originally fitted with an Allison engine, it was later fitted with a powerful British designed V-1650 Merlin engine, producing 1,695 horsepower. The P-51 Model "B" was first used in December 1943. In May 1944, the P-51D was introduced. The Mustang's maximum speed was 437 mph (490 mph for the P-51H), with a cruising speed of 275 mph. The Mustang had a range of 1,000 miles that increased to 1,300 miles for those aircraft equipped with fuel drop tanks and they became wildly successful as escorts for the heavy bombers of the 8th Air Force for missions from England deep into Germany.
As a fighter, the P-51 Mustang had an astonishing success rate. Its ratio for kills to losses was said to have been 19 kills for every 1 Mustang lost. The P-51 Mustang is credited with the destruction of 4,950 German planes, more than any other Allied fighter. Such was the success of the Mustang, that the Senate War Investigating Committee set up by Harry Truman in 1944, called it "the most aerodynamically perfect pursuit plane in existence." "Today the few remaining flying Mustangs can be easily spotted rather heard by the unique sound of the Merlin engine."