Since the very beginning of first commercial flight operations, aircraft mission analysis has played a major role in minimizing costs, increasing performances and satisfying regulations. The operational trajectory of any aircraft must comply with several constraints that need to be satisfied during its operation. The nature of these constraints can vary from Air Traffic Control (ATC) regulations, to emissions regulations and any combination between these two. The development of an integrated tool capable of determining the resources required (fuel and operational time) for a given aircraft trajectory, as well as assessing its environmental impact, is therefore essential. The present work illustrates the initial steps of a methodology developed in order to acquire the optimal trajectory of any specified aircraft under specific operational or environmental constraints. The simulation framework tool is the result of a collaborative effort between Cranfield University (UK), National Aerospace Laboratory NLR (NL) and LMS International (BE). With this tool, the optimal trajectory for a given aircraft can be computed and its environmental impact assessed. In order to simulate the characteristics of a specific trajectory, as well as to evaluate the emissions that are produced during the aircraft operation within it, three computational models developed at Cranfield University have been integrated into the simulation tool. These models consist of an aircraft performance model, an engine performance model and an emission indices model. The linking has been performed with the deployment of the OPTIMUS process and simulation integration framework developed by LMS International. The optimization processes carried out were based on OPTIMUS' built-in optimizing algorithms. A comparative evaluation between an arbitrarily defined baseline trajectory and optimized ones has been waged for the purpose of quantifying the operational profit (in terms of fuel required or operational time) gained by the aircraft operation within the path of an optimized trajectory. Trade-off studies between trajectories optimized for different operational and environmental constraints have been performed. The results of the optimizations revealed a substantial margin available for reduction in fuel consumption as well as required operational time compared to a notional baseline. The optimal trajectories for minimized environmental impact in terms of produced emissions have been acquired and their respective required resources (fuel required and operational time) have been evaluated. Copyright © 2010 by ASME.