Definition
A method of creating a waypoint along an existing RNAV route by specifying a distance from a defined reference fix on that route. The new waypoint lies on the same track as the route, allowing pilots to identify a precise point ahead of or behind a published fix without changing the route's lateral path.
Plain English
Building a new point on your route by saying how far it sits from a fix you already have. The new point stays on the same line you were already flying.
Context Anchor
Seen in area navigation departure procedure design, navigation database coding, and explanations of how RNAV departure waypoints are created.
Derivation
Along track' means 'along the line of flight' — the track being the path the aircraft is following over the ground. The phrase describes exactly what the waypoint is: one constructed somewhere along that existing track.
Why Pilots Care
Allows pilots to understand exactly where course changes and altitude restrictions occur on RNAV departures so they can fly the procedure with precision and predictability.
Grounding Statement
Picture a dot placed a set number of miles down the drawn route line from a known point.
Intuition Check
Do not read “construction” as physical building, and do not read “track” as a railroad-style track. Here, it means mathematically placing a waypoint along the aircraft’s route path.
Example Sentence 1
The crew built an along track waypoint 15 miles before the arrival fix to begin their descent at the right point.
Example Sentence 2
Understanding along track waypoint construction helps the pilot anticipate when the next altitude restriction will appear on the RNAV route.