The results of a systematic comparison of physical models used in the Navier-Stokes computations of high-enthalpy flows over a double cone are presented. The simulations employ various models for the forward reaction rates, the equilibrium constants, the vibrational energy relaxation and the transport coefficients. The comparison of models for transport coefficients shows that their influence on the flow past the double cone is limited and that among all models the Gupta-Yos model for both the viscosity and the thermal conductivity of the mixture gives the best results. This study also shows that all the forward rate constants (Evans, Camac, Gardiner, Park'1985, Park'1990) that are compared in this work produce very similar flowflelds and surface quantities. Similarly, all the equilibrium constant models compared in this work (Park'1985, Park'1990, and the model based on chemical potentials) give the same results. However, none of the results obtained with these various standard models agrees well with the experimental data, unless the chemical rates are artificially tinkered. Therefore, the reason for the discrepancies observed must be linked to the freest ream conditions.