The P-51 Mustang was developed by North American Aviation for the British Royal Air Force after it requested a single-seat fighter to replace the Curtiss P-40. Yet its original incarnation, fitted with an Allison engine, was something of a damp squib, performing poorly at high altitude. The eureka moment came when the British swapped in a new Rolls-Royce Merlin engine, which drastically improved its performance. So much so that it began to dominate Germany’s top fighters, the Me 109 and Fw109.
You could go as far as to argue that its upgrade was a turning point in the war. In October 1943, as many as 9 per cent of the US’ Eighth Air Force bomber sorties credited with attacking their targets failed to return home, while 45 per cent limped back damaged. In 1944, those numbers fell to 3.5 per cent and 29.9 per cent. Suddenly, the Germans lost the fight for aerial supremacy: the P-51 could go deeper into their airspace than any previous aircraft and consistently won dogfights. The RAF alone deployed 1,500 Merlin-powered Mustangs for daylight duties over Europe, while the US fleet ballooned to 13,300.
In truth, the Mustang arrived a touch too late for the RAAF, which built its variant from imported, semi-finished parts. The first production model, A68-1, flew on 29 April 1945 and was used for trials by No 1 Aircraft Performance Unit until October 1946, before being placed in storage. Despite missing WWII, the Mustangs of No 77 Squadron took part in the Korean War from June 1950 until April 1951, before being replaced by Meteors.