Flight Management System — The primary computer system managing navigation, performance, and flight planning in modern aircraft.

The Flight Management System (FMS) is an integrated avionics computer that automates navigation, performance optimization, and flight planning tasks. It is the central 'brain' of a modern aircraft's avionics suite.

Core FMS functions include:

• Navigation: Multi-sensor position computation (GPS, DME/DME, VOR/DME, IRS)
• Flight planning: Route entry, waypoint management, SID/STAR selection
• Performance: Optimum altitude, speed schedule, fuel predictions, cost index computation
• Guidance: Lateral (LNAV) and vertical (VNAV) autopilot commands
• Predictions: ETA, fuel at destination, top of descent, step climb points

Pilots interact with the FMS via the MCDU (Multifunction Control Display Unit) or touchscreen displays on newer aircraft.