The main goal of this Final-Bachelor Project is to develop a version of an in-house Vertical Profile Optimizer, whose optimization will involve the use of optimum speeds which minimize the trajectory cost depending on flight conditions. These speeds will be computed prior to simulations, in order to reduce the computational burden within themselves. Pre-computed speeds will be obtained: through the resolution of an optimal-control problem by means of Non-Linear Programming (NLP), for the phases of climb and descent; and through the numerical resolution of non-linear equations (root-finding) for the phase of cruise. Thus, the greatest weight will be carried by the computation of the tables enclosing the optimal speeds for optimization, tables which will be computed for the most significant aircraft models obtained by means of a clustering process. Eventually, trajectory simulations will be carried out in order to check the efficiency and speed of the new-developed algorithm. Results obtained will be also compared with the ones provided by Airbus' Performance Engineering Program (PEP).