In this paper we present a differential dynamic programming based guidance framework for slung load operations and demonstrate it through simulation studies and a preliminary flight test. Specifically, an optimal control problem is solved with the Differential Dynamic Programming (DDP) algorithm. The resulting optimal vehicle trajectory is used in the vehicle's existing guidance, navigation and control architecture. Furthermore, the state of the slung load is estimated via an augmentation to the existing navigation system that utilizes only vision-based measurements of the load. Therefore, minimal hardware and software changes are needed to an existing system in order to implement the proposed framework. The simulation studies and the preliminary flight test prove that the DDP algorithm can be solved iteratively on-line and is a feasible approach for the control of slung load systems.