In practical engineering, it is often necessary to use models to describe and analyze problems. However, uncertainty exists in the models. There are many models that can describe the same phenomenon, such as the multiple fatigue analysis models. In order to solve the problem of fatigue reliability of aircraft structures, a combination forecasting method based on Bayesian model averaging was proposed by considering three kinds of crack propagation models. Three random crack propagation models were established by using the crack propagation data of aircraft structures under three stress levels. Considering the uncertainty of the model parameters, the Bayesian model averaging method was used to combine the three models. The reliability of the structure was analyzed based on the combined model. The combined model was used to analyze the fatigue reliability of aircraft structure, which can improve the robustness of the results. In addition, considering the uncertainty of the model parameters, more reasonable predictive distribution of crack propagation as well as the reliability can be obtained. Examples and analysis results are given to show the feasibility of this method. 