 When reading performance figures it should always be borne in mind that weight, the aerodynamic drag generated by different external fittings, the condition of the airframe and/or engine, and all sorts of other factors could influence how an aircraft performed.For example, the P-51's laminar flow wings needed to be kept as clean and smooth as possible; even relatively minor damage on the wing leading edges could drastically reduce top speed.The most accurate performance figures for the P-51 came from tests carried out at facilities such as the USAAF's "Flight Test Engineering Branch", based at Wright Field near Dayton, Ohio and, for the RAF, the Aeroplane & Armament Experimental Establishment (A&AEE), based at Boscombe Down.