The initial preventive maintenance interval recommended by civil aircraft manufacturers usually does not consider the operators’ environment and maintenance capacity difference. It is difficult to achieve the optimal state of availability while meeting the requirements of aircraft safety. For the civil aircraft preventive maintenance interval optimization, the reliability model of components is modified by the age reduction factor to reflect the impact of maintenance work on component performance. Combined with the airlines operation reality, taking component availability as the objective function and reliability threshold as the constraint condition, the preventive maintenance interval optimization model in imperfect maintenance strategy is established. The operation data of air starter is input into the optimal model the results show that the model is reasonable and feasible, which provides a reference for airlines to formulate customized maintenance plan.