The term flight management system (or FMCS, flight management computer system) is used to cover some equipment types which have been coming into service in recent years. In this context, it is taken to mean a system for handling horizontal and vertical navigation by various means (as distinct from purely performance management systems).

Such an FMS consists of a computer or computers fed by data from a variety of services, and outputting information and control signals. In horizontal navigation, inputs may be inertial sensors and/or ground-based radio navigation facilities. For performance optimization, data are fed from a number of aircraft systems. This type of system is capable of independently computing several parameters and ‘pooling’ their information to provide a ‘best estimate’. Cockpit information in INS configuration is confined to specific digital displays and data input is, in the main, manual and limited to numerics. FMS goes a number of stages further and provides ‘pre-loaded’ storage of navigational information, and the ability to gain access to this information through an alphanumeric keyboard. It also handles, either directly or through a thrust management computer, the vertical profile of the flight. This includes both climb and descent, and cruise control.