Complex systems are characterized as having multiple interdependent subsystems and requiring the coordination of multiple disciplines to design. Top-level specifications provide the foundation of the conceptual design of such systems. They define system/subsystem concept alternatives, representing the primary descriptors of a complex system. A Robust Concept Exploration Method (RCEM) has been developed to facilitate quick evaluation of different design alternatives and generation of “top-level” design specifications in the early stages of the design of complex systems. Comprehensive exploration of a design space is facilitated through the integration of statistical techniques, robust design simulation, and the compromise DSP. Our focus in this paper is to demonstrate the usefulness of this approach for the conceptual design of a comprehensive and practical industrial example. The preliminary design of a turbine lift engine for Advanced Short Take-Off and Vertical Landing (ASTOVL) fighter aircraft has been defined as a test case through a collaborative project with the Rolls-Royce Atlanta Engineering Group. An overview of our approach is provided; the lift engine example is defined; the steps of this approach, as applied to this example, are detailed and results for different design scenarios are provided and verified.