One component outside of the flow path has an overwhelming influence on performance: it is the electronic controller that is called FADEC (Full Authority Digital Engine Control), EEC (Electronic Engine Control), or DECU (Digital Engine Control Unit), for example. From a performance point of view, the main task of the engine controller is a satisfactory response to the input signal from the pilot. The intended flight segment dictates what he or she wants from the engine. For takeoff, it is the thrust the engine can deliver under the ambient conditions in terms of outside air temperature and altitude. For descent from cruise altitude to landing, for approach or for taxiing from the gate to the runway, it is the minimum thrust. The chapter describes the principles of common thrust management methods and two different approaches. The first is Thrust Rating where one aims for consistent performance, regardless of engine-to-engine variations caused by manufacturing tolerances and time on wing (i.e. deterioration). The second is Full Rating where one aims to extract the maximum performance from each engine, regardless of the manufacturing quality or the level of deterioration. Typically, the first method is applied to engines from commercial airliners while the second method is employed on fighter aircraft engines.