The evolution from raw materials to a ready-to-use car runs through innumerable plants and handling stations. Since the potentials for increasing efficiency in the plant engineering process have largely been exhausted in other areas, the cost pressure in the development or re-engineering of plants is increasing. To monitor and control production processes, manufacturing execution systems (MES) like production monitoring and control systems are developed. Today, the engineering of them takes place at the end of the plant planning process. In most cases, the plant already exists at that time. Recognized errors are very time and cost-intensive. However, this engineering effort can be shifted in earlier phases. MES can be connected to and evaluated against the Digital Factory. In doing so, the full range of features of those systems is available at that time. This contribution deals with preconditions, realization and resulting possibilities of virtual MES start-up within the Digital Factory.