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An Efficient Continuous-Time MILP for Integrated Aircraft Hangar Scheduling and Layout

Created by
  • Haebom

Author

Shayan Farhang Pazhooh, Hossein Shams Shemirani

Outline

This paper proposes a continuous-time mixed-integer linear programming (MILP) that integrates spatial placement and time-continuous scheduling to minimize aircraft maintenance hangar operating costs. It overcomes the scalability limitations of existing approaches by simultaneously optimizing aircraft placement and timing. The proposed model is compared with existing research benchmarks, exploring large-scale performance and quantifying its sensitivity to temporal congestion. It achieves orders of magnitude speedup over literature benchmarks, solving long-standing congested instances in 0.11 seconds and finding proven optimal solutions for instances with up to 40 aircraft. For large-scale problems, it finds solutions with small optimality margins within a one-hour time limit for instances with up to 80 aircraft and provides strong bounds for problems with up to 160 aircraft. The optimized plan consistently increases hangar throughput (e.g., +33% in-service aircraft compared to the heuristic on instance RND-N030-I03), reducing delay penalties and improving asset utilization. These results demonstrate that accurate optimization has become computationally feasible for large-scale hangar planning, providing a validated tool for balancing solution quality and computation time for strategic and operational decision-making.

Takeaways, Limitations

Takeaways:
We present an efficient continuous-time MILP model for the large-scale aircraft maintenance hangar planning problem, overcoming the scalability limitations of existing methods.
Significantly improves throughput (up to +33%) compared to existing heuristic methods, suggesting the potential for increased operational efficiency.
It increases the applicability of the problem by deriving a solution with a small optimality difference within one hour for a problem with a scale of up to 80 aircraft.
Provides proven tools that balance solution quality and computation time through precise optimization.
Limitations:
No optimal solution is guaranteed for problems with more than 160 aircraft (only strong bounds are provided within the 1-hour limit).
The model's performance may be sensitive to temporal congestion. (Sensitivity analysis was performed, but robustness to all types of congestion requires further study.)
It may not fully reflect all the complexities of real-world hangar operations (e.g., unpredictable maintenance times, emergency repairs, etc.).
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