<p>This study investigates the aircraft weight and balance problem (AWBP) of non-Unit Load Devices (non-ULDs) for two-leg flight operations. A weight and balance optimization model is established, incorporating constraints on non-ULDs position allocation, aircraft weight and balance, extra unloading and reloading operations at intermediate airports, and position adjustment. The model aims to minimizing the center of gravity (CG) deviation and the number of extra unloading and reloading operations, while maximizing payload and cargo hold area utilization. To solve the model, a two-stage programming algorithm based on non-ULDs grouping is designed. First, a non-ULDs grouping strategy is developed to combine geometrically similar non-ULDs into larger units, thereby reducing the problem scale. Second, the model is decomposed into two stages: Model 1 focuses on position allocation to resolve geometric conflicts, while Model 2 addresses weight verification and loading and unloading constraints at intermediate airport. Experimental cases using the B747 aircraft consider three transportation scenarios. The results show that the model effectively satisfies weight and balance requirements, reduces extra unloading and reloading operations at intermediate airports, and optimizes aircraft CG, thereby providing a reference for multi-destination transport, emergency rescue, and military logistics applications.</p>