Optimized aircraft maintenance concepts usually aim at increasing the aircraft availability and reducing costs. A model is presented that quantifies the effect of the increased aircraft availability when applying different maintenance concepts on an entire airline fleet. An agent-based approach is suggested: The aircraft with their maintenance tasks are dynamically assigned to the flight schedule. One major advantage of the presented methodology is that constraints for specific aircraft tails can be added easily. This is potentially of interest when testing new maintenance concept that are more focused on optimizing maintenance for single aircraft, by e.g. a stronger dependency on aircraft usage and findings.