In the future Air Traffic Management (ATM) implementations based on 4D trajectories, both the ATM problems (safe separation, sequencing for the best runway utilization) and the flight management problems (best fuel efficiency) may be solved together using a multidisciplinary optimization of all aircraft 4D trajectories. The paper presents advancements on 4D navigation based on an objective function for the optimization process, which effectively models the total costs and risks of air navigation. The resulted gate-to-gate 4D trajectories generated by a dynamic model flight simulator for the specific type of aircraft with the individual initial Flight Management System data are "flyable", and they present the best cost-risks trade-offs. The paper also reveals results on some simulated experiments using genetic algorithms to minimize the objective function presented. Nomenclature C = c o s t C D = coefficient of drag 1 Associate Professor, Faculty of Aerospace Engineering, otp@brainbond.ro, Member AIAA. 2 Associate Professor, Faculty of Aerospace Engineering, constantinescu_ce@yahoo.com 3 Researcher, irina.stefanescu@rosa.ro