Abstract—The processes of heat transfer and air ionization in gas flow in the neighborhood of blunt plates of bluntness radii Rn = 0.2 and 0.66 cm are simulated numerically over a wide free-stream-parameter range. The temperature fields of the translational and vibrational degrees of freedom of molecular components and the number densities of atomic and molecular components as well as the electron number densities in the neighborhood of the surface are constructed. The convective heat flux densities calculated are compared with the data predicted by the Fay–Riddel, Detra–Kemp–Riddel, and Fenster correlation relations. In the cases considered the volume fraction of ionized components is not greater than 1%. However, the regimes of strong and weak ionization are distinguished. In the present study the boundary between the two regimes is determined from the critical electron number density found for the radio-wave frequencies of 3.3–35 GHz used in the RAMC-2 flight experiment to measure the electron number densities.