Biological nitrogen fixation (diazotrophy) in aerobes is an issue due to the sensitivity of nitrogenase enzyme to oxygen. In this study, the respiratory system of Azotobacter vinelandii and its effects on growth, nitrogen fixation, and respiratory protection of nitrogenase were investigated by reconstructing two models (respiratory and growth) and applying flux balance analysis. Simulation of the respiratory system revealed a progressive increase in energy-conservation efficiency across the terminal oxidases in the order of bd, cbb₃, and aa3-like. In growth simulations performed with succinate uptake constrained at 3.5 mmol gDW⁻¹ h⁻¹, the bd pathway resulted in the lowest specific growth rate (0.125 h⁻¹) and the highest oxygen uptake rate (6.168 mmol gDW⁻¹ h⁻¹). In contrast, activation of the aa3-like pathway yielded the highest specific growth rate (0.157 h⁻¹) and the lowest oxygen uptake rate (4.608 mmol gDW⁻¹ h⁻¹). The elevated oxygen consumption associated with the bd pathway led to reduced growth rate while enhancing respiratory protection of nitrogenase. Within the constraints of the model, the distinct performance of the terminal oxidases reflects a trade-off among oxygen consumption, energy-conservation efficiency, and the availability of carbon substrates and reducing equivalents within the metabolic network.