Definition
White painted stripes at the beginning of a runway's landing surface that identify where the usable landing area starts. They appear in two patterns: eight longitudinal stripes of uniform dimensions arranged symmetrically about the runway centerline, or a number of stripes that corresponds to the runway width.
Plain English
The set of long white stripes painted across the start of a runway, showing pilots exactly where they are allowed to touch down.
Context Anchor
Seen during landing, especially near the end of an instrument approach when the pilot must visually identify the runway environment before continuing below minimum altitude.
Derivation
Threshold comes from the Old English 'therscold,' meaning the doorway or entry point to a building. On a runway, the threshold is the doorway into the landing surface — the line where the usable runway begins.
Why Pilots Care
Correct recognition confirms the available landing distance and prevents landing short of the prepared surface.
Intuition Check
Do not read threshold markings as just any paint near the end of a runway. In this context, they are the specific white runway markings that show the start of the usable landing area.
Example Sentence 1
On short final, the pilot aimed to cross the threshold markings at fifty feet and touch down just beyond them.
Example Sentence 2
In reduced visibility the threshold markings remained visible and helped establish the touchdown zone.