With the rapid growth in passenger transportation through aviation projected to continue into the future, it is incumbent on aerospace engineers to seek ways to reduce the negative impact of airliner operation on the environment. Key metrics to address include noise, fuel consumption, Carbon Dioxide and Nitrous Oxide emissions, and contrail formation. The research presented in this paper generates new aircraft trajectories to reduce these metrics, and compares them with typical scheduled airline operated flights.Results and analysis of test cases on trajectory optimization are presented using an in-house aircraft trajectory optimization framework created under the European Clean Sky Joint Technology Initiative, Systems for Green Operation Integrated Technology Demonstrator. The software tool comprises an optimizer core and relatively high fidelity models of the aircraft's flight path performance, air traffic control constraints, propulsion and other systems. The tool includes models to predict noise, emissions and contrail formation.The results report horizontal and vertical trajectories for a long haul flight from London Heathrow to Colombo in Sri Lanka. Particular studies have been conducted on contrails formation during flight in the cruise segment, as well as the impact of conventional and more electric systems penalties on the aircraft's performance. Minimum noise and minimum fuel burn criteria are objectives in the optimization of the departure and arrival segments. Minimum time and minimum fuel burn are used in the optimization of the en-route segments, together with the contrails optimized routes for comparative assessment.The solutions of optimized trajectories are presented in terms of flight profile charts for the altitude and speed. The environmental gains between the investigated criteria, in each flight segment, are presented based on the results obtained using the framework.