Holdover time (HOT) guidelines for de-icing and anti-icing aircraft

The holdover time (HOT) guidelines provide estimates of how long aircraft anti-icing fluids will be effective. They help aircraft flight crews make decisions when de-icing and anti-icing an aircraft on the ground.

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Current HOT guidelines

About the HOT guidelines

We update and reissue HOT guidelines every year. Sometimes we publish a revision in the same year.       

These guidelines contain tables with explanatory notes. These tables provide aircraft flight crews with safe holdover times given the following criteria:

  • Air temperature
  • Type of precipitation
  • Rate of precipitation
  • Type of de-icing or anti-icing fluid

Normally, aircraft should not take off after the holdover time has expired. Aircraft may take off only after either:

Refer to the Guidelines for Aircraft Ground-Icing Operations (TP 14052) when using the HOT guidelines.

Archived HOT guidelines

The following guidelines are no longer used. We provide them for informational purposes only. If you require an alternative format, please contact us.

Regression information documents

To calculate more precise holdover times than those presented in the HOT guidelines, several companies manufacture and use HOT determination systems (HOTDS) to measure real-time temperature, precipitation type and precipitation rate. HOTDS use:

  • weather data they collect
  • regression information we provide

Each year, we make available a regression information document for these HOTDS manufacturers. It contains regression information, verification tables and guidance for the current HOT guidelines. To request the most current document, please contact us.

Contact us

Civil Aviation Communications Centre

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