Online Simulation builds on physically-sound first principal models. Compared to conventional simulation approaches, in Online Simulation the models are executed live, simultaneous to production. This presentation gives insight on Online Simulation at Covestro. For several case studies, value for troubleshooting, KPIs and optimization is discussed. While Covestro has been operating Online Simulation for about twenty years, persisting challenges are highlighted which lead to two specific opportunities ahead: (1) AVEVA Process Simulation is investigated as an alternative tool for simulation offering various advantages of a modern simulation software. (2) The newest Asset Framework (AF) can allow for deeper integration with plant operation. In conclusion, new tools such as AVEVA Process Simulation and AF can help overcome persistent challenges and provide deeper integration with plant operation and monitoring of KPIs.