We construct a simulation model for the use of a fleet of Bae Hawk Mk51 aircraft during their normal operational use. The model describes the flight policy and the main factors of the maintenance, failure, and repair processes. On one hand, the model aims at a better understanding of the critical paths in the normal service activity, and thus helps, e.g., in shortening the turnaround times in the maintenance. Model implementation with graphical simulation software allows rapid what-if analysis for maintenance designers. More importantly, since the model can be verified, validated, and accredited using existing statistical data, it provides information on the level of detail on which such processes should be modeled. This information, together with sensitivity analysis results and expert knowledge can be used in the further development of the model to describe special circumstances for which statistical validation data is not available.