IFATCA takes the view that SI (Système International d’Unités) is not necessarily providing a single solution for Civil Aviation, and that, in order to obtain a common global standard which is necessary for safety reasons, then specific non SI elements should be retained for the measurement of Vertical Distance, Speed and Distance.

IFATCA Policy is:

IFATCA supports a global standard for the measurement of vertical distance, speed and distance.

IFATCA supports the following units of measurements be used as the global standard:

  1. for vertical distance: FEET; (Vertical distance is altitude, elevation and height)
  2. for vertical speed: FEET PER MINUTE;
  3. for horizontal speed: KNOTS;
  4. for long distances*: NAUTICAL MILES.

* long distance used in navigation generally in excess of 4000 metres.

Any change in use of current units of measurement should only be implemented after appropriate training of controllers.
See: WP 100 – Marrakech 2000, Resolution B13 – WP 102 – Bucharest 2026

 

Last Update: 19th May 2026
4th November 2019 963 Jean-Francois LepageATSTOC , ATS , TPM , ATM Operations

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Jean-Francois Lepage

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