TDZE – THRE – Touchdown Zone – Threshold

In a field with a lot of technical terms and concepts, such as aviation, some terms are likely to be confusing. Let’s look at the concepts of Threshold elevation (THRE) and Touchdown zone elevation (TDZE).

What is Touchdown zone?

The portion of a runway, beyond the threshold, where it is intended landing aeroplanes first contact the runway. – Source: ICAO Annex 14

What is threshold?

The Runway Threshold is the position across the runway that denote the beginning and end of the designated space for landing and takeoff under non-emergency conditions.

What is Displaced Threshold?

A threshold not located at the extremity of a runway. – ICAO Annex 14

What is Runway?

Defined rectangular area on a land aerodrome prepared for the landing and takeoff of aircraft. – ICAO doc4444


The TDZE is defined as the highest elevation in the first 3000 feet of the runway starting at the threshold.

So, if Threshold consists the highest point in Touchdown zone area, TDZE = THRE.

Airport Layout - Touchdown zone
Airport Layout

Understanding these aviation terms is like deciphering the secret language of pilots. So, the next time you hear “Touchdown Zone” and “Threshold,” remember this: they’re partners in precision, ensuring every landing is a graceful touchdown, not a bumpy touchdown. Now go forth and conquer the skies (metaphorically, of course)!

References and Further Reading

What is Turn Pad on Runways?