A stacker adapted to generally stack product in a vertical fashion is provided. The stacker includes a first generally vertical conveyor having a first conveyor belt and a first plurality of flights mounted generally perpendicularly to the first conveyor belt. The first plurality of flights at least partially defines a plurality of stacking platforms. At least one positioning sensor for sensing a relative position of the flights is provided. An advancement sensor is provided for sensing product entering the stacker. A first drive incrementally drives the first conveyor responsive to the advancement sensor so that the stacking platforms descend. Each of the stacking platforms can receive individual or single items to be stacked into a tray or can sequentially receive multiple items, either pre-stacked or stacked on a given flight, and then be indexed downwardly to allow the next stack to be formed on the subsequent stacking platform. A method and system for handling and stacking products is also provided.