Touchdown Zone (TDZ)
The touchdown zone (TDZ) is the portion of a runway, beyond the threshold, intended for initial contact of landing aircraft. For precision runways, it extends 3,000 ft from the threshold (or to the midpoint of the runway if shorter). The TDZ is marked by white rectangular bars on each side of the centreline.
Why the TDZ Matters
Landing before the threshold or far beyond the TDZ reduces the effective runway available for deceleration. The approach and ILS glide slope are designed to place the aircraft in the TDZ. Consistently touching down in the TDZ is a measure of approach precision.