Calculations of the gasdynamic parameters of air using different equations of state for a real gas in one-dimensional formulation were carried out in [1-3]. The results from these papers are of a limited nature, as the equation of state of a real gas, which occurs in the system of starting equations, is valid for a quite narrow range of total pressures and temperatures. In [4, 5], a semiempirical equation of state is proposed, which was used in [6, 7] for investigating the isentropic expansion of air and nitrogen. A method is proposed in this paper for calculating the parameters of air during its isen tropic expansion from high stagnation pressures, using the semiempirical equation of state proposed in [8]. Flow calculations are carried out for air at stagnation pressures p = 10-900 bars and stagnation temperatures T = 220-450~ over the range of Mach numbers M = 0 to 6. Over the stated wide range of stagnation parameters, where the effect of van der Waals forces is large, the calculations indicate a significant change of the dimensionless gasdynamic parameters of air as a function of the absolute values of the stagnation pressure and temperature. The experimental data confirm the accuracy of the results of the calculations.