We consider a flexible manufacturing facility that can be operated in nay of $m$ different modes. While running in mode $k$ certain intermediate products are consumed and other intermediate or finished products are created. There may be variability in the manufacturing process, as well as random arrivals of raw materials and orders for finished products. We establish conditions that ensure demands can be satisfied while maintaining bounded levels of inventories. These results may be viewed as generalizing to the flexible manufacturing context the notion of stability for a queueing system.