The threshold is the official start of the runway surface available for an aircraft to touch down. It is marked by a series of thick white stripes painted across the pavement. If there are obstacles on the approach path, the threshold may be displaced further down the runway to ensure a safe glide path.
Heard on the job
Aim for the touchdown zone markers just past the threshold.
Insider tip
A displaced threshold can be used for taxiing and takeoff, but never for landing.