Impacts of various types of O/F shifts on flight performances of a single stage sounding rocket with a scale of S-520 sounding rocket series were comprehensively evaluated by flight simulations of O/F controlled and uncontrolled hybrid rockets. Before the simulation, sources of O/F shifts and factors affected by O/F shifts were classified and discussed in order to clarify the respective sets of simulations. O/F shifts along with the median fuel regression rate behaviors, systematic errors of the behaviors, and random errors of fuel regression rates were statistically modelled using multiple regression theroy. Shifts of thermodynamic states of productive gases after combustion, shifts of c∗efficiency, and nozzle throat erosion were modelled as factors affected by O/F shifts. Operations of propulsion systems were assumed to include throttling. In the presence of O/F shifts along with a median regression rate equation, shifts of thermodynamic states of productive gases were the dominant factor causing performance losses of O/F uncontrolled rockets. In the presence of systematic or random errors of fuel regression rates, residuals of propellants were the other dominant factor to decrease flight performances. Especially in the random error cases, as a result of 3000 times of flight performances, the guaranteed highest altitude of the O/F controlled rocket was 5.2% higher than that of uncontrolled rocket within ±3σ. This result shows that the O/F controlled hybrid rockets have about 2.6% higher acceleration than the O/F uncontrolled rockets. Accuracy of acceleration of the O/F controlled hybrid rocket was 10 times higher than that of the O/F uncontrolled hybrid rocket. These results indicate that the significance of O/F shifts elimination of hybrid rockets from both the aspects of expectancy and accuracy of flight performances.