This course is dedicated to energy management, i.e. speed and altitude control. The various sources of drag are first described and modeled, as well as thrust origin, and evolution with speed and altitude. Using these models, we can evaluate the propulsive balance and derive important concepts like flight regimes, best climb speed, or propulsion ceiling. We take then a glance at cruise performances and the evolution of range with weight. This course is a part of the specialization "Fundamentals of Flight mechanics".