Based upon the feasibility demonstrated in the Phase I research, Optimal Synthesis Inc.(OSI) proposes to develop a software tool that can be used validate aircraft flight deck user interfaces over the entire flight envelope. The approach is based on a mathematical formalism derived from hybrid systems theory. The correctness of information content in user interfaces is analyzed by a special observability test that takes into account of the limitations in human cognition and psychology. A possible mismatch between an operational mode perceived by the human operator and the one active in the aircraft is detected using an algorithm that compares the inferred intent of the human operator to that of the machine. Metrics-based performance evaluation will be carried out to demonstrate the benefits of the prototype software developed under the Phase II research. The feasibility of employing the software on the flight deck as a real-time pilot aid will also be analyzed in the Phase II research.