Definition
A solid white transverse stripe, ten feet wide, painted across the full width of a runway to mark the beginning of the landing surface when the threshold has been relocated from the physical end of the pavement. Pavement before the threshold bar is not available for landing.
Plain English
A thick white line painted across the runway showing where the part you are allowed to land on actually begins. The paved area before that line cannot be used to touch down.
Context Anchor
Seen on runways where the normal landing starting point has been moved, especially with a displaced or relocated runway threshold.
Derivation
‘Threshold’ comes from Old English meaning the strip of wood or stone at the bottom of a doorway — the point where you cross from outside to inside. On a runway, the threshold is the line where the usable landing surface begins. The ‘bar’ is simply the painted stripe that marks it.
Why Pilots Care
Pilots use the threshold bar to determine the actual start of the runway for calculating landing and takeoff distances, which may be shorter than the full runway length.
Intuition Check
Do not picture a physical gate or raised barrier. A threshold bar is a painted runway marking, and it marks where the landing portion begins.
Example Sentence 1
On final approach, the pilot aimed past the threshold bar to ensure the wheels touched down on the usable landing surface.
Example Sentence 2
With the threshold bar marking the new beginning, the available landing distance was reduced by 800 feet.