The paper presents results of computational simulation of the high-speed airflow around an axisymmetric body using various models that include ideal gas described by the Mendeleev—Clapeyron equation, real gas described by the Redlich—Kwong equation and user model approximating the empirical data. The user model is characterized by its own program code for the two-parameter approximation of the air thermophysical properties and taking into account in this context changes accompanying dissociation phenomena occurring at high temperatures without simulating physical and chemical transformations in the multicomponent gas mixture. The purpose of this study is to evaluate differences in the gas-dynamic flow pattern, shock-wave structure and thermal loading of the streamlined body depending on selection of the medium model. The results obtained make it possible to conclude on the need to introduce the real gas user models to reduce the error of computational simulation and ensure correct estimation of the heat flows.