As the speed of a hypersonic vehicle increases, atomic emission lines in the shock-layer will be a main source of radiative heating. Therefore, it is very important to study the atomic excitation in the air plasma in the shock layer. For a thermal nonequilibrium air plasma, the equilibrium statistical theory is not applicable. Although full models (such as the collisional-radiative model) can be used to solve nonequilibrium problems with high accuracy, they are too expensive computationally and difficult to apply to engineering. In this work, we investigate the atomic excitation in air plasmas by the bound-state characteristic temperature (BCT) method. Some cases of equilibrium and nonequilibrium air plasmas associated with the well-known FIRE II flight experiment are considered. The calculated atomic energy level populations are in good agreement with those from the CR model, thereby showing that our calculation is reasonable and has a good accuracy. The computational efficiency is more than 2000 times higher than that from the CR model. If it is used in the flow field of a hypersonic vehicle, the computational cost can be greatly reduced.