Definition
An air traffic management approach in which each aircraft is managed according to a four-dimensional trajectory — latitude, longitude, altitude, and time — that is shared and coordinated between the aircraft and air traffic control. Rather than controlling traffic primarily through tactical clearances and radar vectors, controllers and pilots work from an agreed flight path that includes when the aircraft will be at each point along the route.
Plain English
A way of running air traffic where every flight follows a planned path through the sky that includes not just where it goes, but exactly when it will be at each point. Controllers and pilots agree on this path in advance and stick to it, instead of the controller telling the pilot what to do step by step.
Context Anchor
Seen in discussions of modern air traffic control, flight planning, route changes, arrival flow, and controller-pilot coordination.
Derivation
Trajectory comes from the Latin trajectus, meaning 'thrown across' — the path an object follows through space. In this term, the trajectory is treated as a precise plan to be followed, not just the path that happens to result. The 'based' part means the whole operation is built around this planned path rather than around moment-to-moment instructions.
Why Pilots Care
It enables more direct routes, lower fuel use, fewer delays, and greater airspace capacity once fully implemented.
Grounding Statement
The key idea is that the system is not just watching where an aircraft is now; it is using a shared plan for where that aircraft should be later.
Intuition Check
Do not read “trajectory” here as only a line drawn behind or in front of the airplane. In this term, the trajectory includes both the route through the air and the timing along that route.
Example Sentence 1
Under Trajectory-Based Operations, the crew was expected to cross the waypoint within a 30-second window of the agreed time.
Example Sentence 2
Trajectory-Based Operations allow dispatchers to plan fuel loads more accurately by predicting exact arrival times.