A hierarchical approach to planning production in complex manufacturing systems is presented. A single facility containing a number of work-centers that produce multiple part types is considered. The planning horizon includes a sequence of time periods, and the demand for all part types is assumed to be known. The production planning problem consists of minimizing the holding costs for the work-in-process and finished goods inventory and the backlogging costs for unfulfilled demand. We present a two-level hierarchy that is based on aggregating part types to part families, work-centers to manufacturing cells and time periods to aggregate time periods. The solution of the aggregate optimization problem is imposed as a target in the optimization problems at the detailed level. This architecture uses a rolling horizon strategy to manage production.