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
Mach Five protagonists build the Mach 6. The Mach 6's engine is not designed to run on gas, which is a crucial story point, even though gas is still used for it through most of the series. It has all the features of the Mach Five, but redesigned or changed in some form or another. For example, the rotary saws are kept, but they're turned into laser saws, and the blades can pivot so things that are over head can be cut. The new car features a transparent, holographic screen over the dashboard that the driver can use to interact live with