Mach number which was also unit-first, and may have influenced the use of the term Mach. In the decade preceding faster-than-sound human flight, aeronautical engineers referred to the speed of sound as "Mach's number", never "Mach 1". Mach number is useful because the fluid behaves in a similar manner at a given Mach number, regardless of other variables. As modeled in the International Standard Atmosphere, dry air at mean sea level, standard temperature of , the speed of sound is . The speed of sound is not a constant; in a gas, it increases as the absolute temperature increases, and since atmospheric
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.