Unit Load Devices (ULD) are standard equipment for loading baggage and cargo on aircraft. Maintaining their own ULD stock is a significant cost factor for airlines. In recent years, many airlines have therefore outsourced the management of their ULDs to independent ULD providers.

Unilode Aviation Solutions (formerly Unitpool) is a globally active ULD provider. At the time of the project, the company employed over 400 people and managed approximately 200'000 ULDs at over 300 airports on all continents. Operational control of the units took place around the clock at the Global Operations Centre in Bangkok.

Unilode Aviation Solutions needs to provide its airline customers with a sufficient number of ULD's at the airports. Until recently, the control of ULD's in the global flight network was based on the experience of manual planners. The growing number of ULD units made the daily operational planning increasingly complex.

Therefore, decision support tools for calculating the daily ULD safety stock levels have been developed in the context of an applied research project. For a defined planning horizon, the aim is to guarantee the availability of sufficient ULD units to provide a specified level of service. In addition, an optimized ULD control logic has been designed to balance inventories at airports through systematic ULD transfers.

In order to determine the safety stocks, a software has been built that simulates the future flight movements based on the historical data. The control of the ULD's is realized by a suitable transport optimization model. The developed models have been integrated into the company's existing software, are used on a daily basis and access the operational database directly. The calculated safety stocks are analyzed by ULD managers and support them in their daily decisions.