The assignment of cargo shipments to available capacity is a complex process. Shipments that vary greatly in weight, volume, and shape must be loaded into Unit Load Devices (ULDs). A slight overestimate of the required number of ULDs can be very costly in terms of delayed cargo. This paper presents a decision-support tool that provides packing strategies for the handling & operations department of a cargo airline. At regular intervals, advice is provided concerning: when to build up a ULD, what items to place in the ULD, and where to place the items within the ULD. As the model considers all flights handled by the warehouse, it is able to optimize operations on a macro-scale rather than an individual flight level. The scheduling of build-up requires accurate information on the availability time of cargo at the warehouse. to deal with uncertainty inherent to such availability, bespoke machine learning prediction models are developed which can provide prediction distributions rather than point estimates. The performance of the model is evaluated through a simulation with real-world data from historic operations of a partner airline. Particularly, the effects of the uncertainty of cargo arrival times on loading performance is investigated. The method to deal with this uncertainty is implementing staff buffer as a contingency. The tool can analyse the cost and benefit of introducing staff buffer to find the optimal amount for each scenario.