Definition
A flight display concept that shows the pilot a three-dimensional representation of the desired flight path, typically rendered as a series of boxes, rings, or a pathway projected on a primary flight display or head-up display. The pilot flies the aircraft so that it passes through each box or follows the depicted corridor, providing intuitive guidance for course, altitude, and vertical profile in a single visual reference.
Plain English
A picture on the pilot's display that shows the planned flight path as a road or chain of boxes hanging in the air. The pilot just flies through the boxes to stay on course and at the right altitude.
Context Anchor
Seen on some modern flight displays, simulator displays, and synthetic-vision systems that guide a pilot along a planned route or approach path.
Derivation
The name is a plain-English metaphor: the guidance is presented as if a 'highway' were drawn through the sky for the pilot to follow. The phrase entered aviation use as graphical flight displays became capable of rendering a 3D path in real time.
Why Pilots Care
It simplifies navigation and reduces pilot workload by providing intuitive visual guidance, improving safety and precision especially in low visibility conditions.
Analogy
Like the navigation arrows a satnav projects onto a car windshield, except the arrows form a continuous tunnel through the sky that the aircraft flies through.
Intuition Check
Do not take the phrase literally: it is not a real road in the sky and not a separate legal route by itself. It is a display that visually guides the pilot along the intended flight path.
Example Sentence 1
On the synthetic vision display, the highway in the sky guided the pilot through the curved RNAV approach without needing to cross-check raw course data.
Example Sentence 2
Advanced avionics project the highway in the sky to assist with precise RNAV procedures.