This paper deals with the proper formulation of the macroscopic equations of high temperature hypersonic flow in the presence of nonequilibrium phenomena such as vibrational, rotational and electronic excitation, dissociation, ionization, and thermal radiation. A multi-group model based on the maximum entropy principle is presented. Quantum states of each species are divided into groups. Translational equilibrium but thermo-chemical nonequilibrium among groups is assumed. The internal temperature of each group is proportional to the inverse of the Lagrange multiplier for the total internal energy constraint for that group to reach maximum entropy. Macroscopic equations for group population and internal energy are derived from moments of the master equations. Microscopic rate coefficients are obtained from a quasi-classical trajectory method or a quantum dynamics method. Macroscopic group rate coefficients for internal excitation, dissociation, ionization, internal energy - translational and radiative energy exchange, and internal - chemical reaction coupling are then determined. The proposed model allows all possible collisional and radiative transitions. Current vibrational nonequilibrium models and collisional-radiative models are special cases of the proposed model.