Mach number temperature generally decreases with increasing altitude between sea level and , the speed of sound also decreases. For example, the standard atmosphere model lapses temperature to at altitude, with a corresponding speed of sound (Mach1) of , 86.7% of the sea level value. While the terms "subsonic" and "supersonic", in the purest sense, refer to speeds below and above the local speed of sound respectively, aerodynamicists often use the same terms to talk about particular ranges of Mach values. This occurs because of the presence of a "transonic regime" around M = 1 where approximations of the Navier-Stokes equations used
Ford Mustang Mach 1 tendency to understeer more than the IRS equipped SVTs and lower CG and lower curb weight Bullitt GTs with the same basic suspension and brakes. Limited in production, the 2003 and 2004 Mach 1s ended with the New Edge body platform, the discontinuation of the Fox framed unibody, and the introduction of the first new frame design since 1979 the s-197 with 9,652 2003's and 7,182 2004's being built, contrary to the Mach 1 originally being advertised as a one-year limited run model with production set at 6,500 cars. The Mach 1 nameplate could possibly make a return in 2018.