Vehicle design is a complex process requiring interactions and exchange of information among multiple disciplines such as fatigue, strength, noise, safety, etc. Simulation models are employed for assessing and potentially improving a vehicle's performance in individual technical areas. Challenges arise when designing a vehicle for improving mutually competing objectives, satisfying constraints from multiple engineering disciplines, and determining a single set of values for the vehicle's characteristics. It is of interest to engage simulation models from the various engineering disciplines in an organized and coordinated manner for determining a design configuration that provides the best possible performance in all disciplines. The multi-discipline design process becomes streamlined when the simulation methods integrate well with finite element or computer aided design models. This paper presents an approach that conducts optimization analysis for a complex system by coordinating operations and exchange of data and information through a network of optimizations. The presented approach provides an organized and seamless environment that captures the implications of design changes from a particular discipline to all other disciplines. It is possible to share design variables among disciplines and thus identify the overall direction that design variables should follow based on objectives and constraints from multiple and often mutually competing requirements. The Hybrid Finite Element Analysis (Hybrid FEA) is a method developed for mid-frequency structure-borne vibro-acoustic simulations. It combines conventional finite elements for modeling the frame structure and the in-plane behavior of panels with energy finite elements for modeling the flexible behavior of the panels. Since the simulations are based on a finite element model, the method integrates well in a multi-discipline design process. A rotorcraft example that demonstrates the operation of an integrated design environment and the utilization of the Hybrid FEA is discussed.