Aviation industry has been undergoing a deep transformation in recent years. The main focus in civil aviation industry is nowadays the environmental impact. One possible solution is to address the emissions concern is to move towards moreelectric architectures. One of the main problems in Hybrid-Electric Architectures is waste heat produced by the electric devices. As higher powers are required, more waste heat is produced: a good waste heat management system is required to move towards more-electric architectures. For this reason, having a good Thermal Management System (TMS) design is vital. To achieve better TMS architectures, new design challenges must be addressed: integrating Model-Based Design and Multi-Disciplinary Optimization with system dynamic simulations may be an option to enhance the design process.