Definition
A standard ATC phraseology used during a precision approach (such as an ILS or PAR) to inform the pilot of the aircraft's vertical position relative to the published glide path. 'On glide path' means the aircraft is tracking the correct descent angle to the runway. 'Above glide path' means the aircraft is higher than the prescribed descent profile. 'Below glide path' means the aircraft is lower than the prescribed descent profile and may need to reduce its rate of descent or climb to regain it.
Plain English
A controller's way of telling the pilot whether the aircraft is right on the correct descent slope to the runway, too high, or too low.
Context Anchor
Seen during approaches to a runway, especially when using visual or instrument guidance that helps the pilot stay on the correct descent angle.
Derivation
Glide' comes from Old English 'glīdan,' meaning to move smoothly. 'Path' is the route being flown. Together, the glide path is the smooth descending route the aircraft follows down to the runway.
Why Pilots Care
Staying on the glide path provides obstacle clearance and positions the aircraft for a safe touchdown; deviations can lead to runway undershoot or overshoot.
Analogy
It is like following a sloped driveway down to a garage. If you are on the driveway, you are lined up with the slope; if you are above or below it, you are not following the intended path.
Grounding Statement
Picture an invisible sloping line from the airplane down to the runway touchdown area; the aircraft can be on that line, above it, or below it.
Intuition Check
“On” does not mean simply over the runway or lined up left-to-right. Here it means vertically aligned with the intended descent path.
Example Sentence 1
The controller advised, 'Cessna 12X, on glide path, on course,' confirming the approach was tracking correctly.
Example Sentence 2
PAPI lights showed two white and two red, placing the aircraft slightly below the glide path.