Critical Mach number and slow down as it travels around the aircraft's structure. When the aircraft's airspeed reaches the critical Mach number, the speed of the airflow in some areas near the airframe reaches the speed of sound, even though the aircraft itself has an airspeed lower than Mach 1.0. This creates a weak shock wave. As the aircraft exceeds the critical Mach number, its drag coefficient increases suddenly, causing dramatically increased drag, and, in an aircraft not designed for transonic or supersonic speeds, changes to the airflow over the flight control surfaces lead to deterioration in control of the aircraft. In aircraft
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.