We are developing a kinetic Fokker-Planck (FP) method to complement our existing computational fluid dynamics (CFD) code for aerodynamic and aerothermal simulations of space applications. The FP method is capable of simulating problems at low atmospheric densities, where the continuum assumptions of the CFD lose their validity. The FP method solves the Boltzmann equation and has the additional benefit of being computationally effective for low Knudsen numbers when compared to the Direct Simulation Monte Carlo method (DSMC). The FP method has been extended to model internal degrees of freedom using the Master Equation Ansatz for diatomic molecules as well as mixtures. In order to validate the new FP implementations and to better understand the limits of CFD and FP, we are simulating an upper stage, as a large test case. In this work we continue previous investigation with CFD and FP of upper stages, by expanding the modelling from single species diatomic \(N_2\) gas to representing air as a gas mixture. We introduce the underlying simulation methods and explain the relevant differences. We compare the resulting flow fields.