A new generation of aerospace systems has introduced more-electric technologies and highly coupled architectures, leading to a substantial increase in design complexity. The inability of current design systems to manage this complexity has lead to substantial cost and schedule overruns during the development of new military and commercial platforms. This paper presents the framework for a new design process to manage system complexity and highlights four key elements: 1) Abstraction-based design tools to allow complex interactions to be assessed at a high level of abstraction early in the design cycle; 2) Quantitative complexity metrics that can guide early design decisions and identify sources of complexity within candidate designs; 3) Advanced architecture synthesis methods that enable the formal and automated architecture synthesis, enumeration, and evaluation of feasible architecture options; and 4) Robust uncertainty management for identifying strong coupling between systems with high uncertainty, thereby allowing the identification and management of key risks.