Mach number a small area around the object's leading edge. (Fig.1b) Fig. 1. "Mach number in transonic airflow around an airfoil; M < 1 (a) and M > 1 (b)." When an aircraft exceeds Mach 1 (i.e. the sound barrier), a large pressure difference is created just in front of the aircraft. This abrupt pressure difference, called a shock wave, spreads backward and outward from the aircraft in a cone shape (a so-called Mach cone). It is this shock wave that causes the sonic boom heard as a fast moving aircraft travels overhead. A person inside the aircraft will not hear this.
Ford Mustang Mach 1 (without Ram Air) remained optional on every model. Chart does not reflect the Boss 351 variant of the 351 Cleveland or 250cid I6, as neither were available in the Mach 1 package. The 1972 R-code 351HO package - essentially the solid-lifter Boss 351 motor from 1971 with a reduction in compression from 11.0:1 to 8.8:1 - is listed here, as it was available with the Mach 1 package that year. The Mach 1 name continued with the advent of the Mustang II in 1974. The downsized vehicle - fitted with the 2.8 L V6 rated at - outsold the Mach