Operational aspects of a functionally integrated automatic flight path and speed control autopilot are discussed. A system is described using point mass energy principles to develop coordinated elevator and thrust commands and provide decoupled flight path and speed control for all the traditional autopilot and autothrottle functions. Various aspects of this integrated multi-input/multi-output system design on performance, operational capability, system architecture and redundancy requirements, hardware and software requirements are described. Also, possible mode control panel functional design improvements are discussed. Feedback signal normalization into energy related quantities is shown to be the key to achieving natural control decoupling with desired energy management features and consolidation of all computations for fully automatic control, computer augmented manual control and flight director thrust/elevator control guidance displays. The design approach offers overall design coherency and simplicity.