Accessing and calculating holdover times is now easier with the APS Holdover Times app

Two Ways to Obtain Holdover Times
Holdover Times

PDF Viewer

Use the PDF viewer to access the Transport Canada, FAA and AEA holdover time documents electronically without an internet connection. The PDF Viewer divides the holdover time documents into individual PDF files which are sorted into categories for easy navigation and viewing. All tables and guidance contained in the holdover time guidance documents are accessible using the PDF Viewer. Related guidance documents for each authority are also provided.


HOT Calculator

Calculate the holdover time for current conditions by entering the applicable authority, weather information, and fluid information. The appropriate holdover time will be provided, along with all related notes and cautions and the applicable holdover timetable PDF. Use the “HOT Clock” and related graphics to keep track of the status of your holdover time: The status bar fills in as the holdover time is used up and the traffic light alerts you to your status within the holdover time range:

  • Green light: below lowest HOT in range
  • Yellow light: between lowest and highest HOTs in range
  • Red light: longest HOT in range exceeded

The HOT Calculator incorporates lowest operational use temperatures (LOUTs) for Type II, III and IV fluids for FAA and Transport Canada and provides an alert when the air temperature entered is below the LOUT.


Frequently Asked Questions (FAQs)

We have put together a list of the most common questions asked by our users. If your question isn’t answered here, please contact us at


What qualifies APS Aviation to create this app?

We are the world's leading experts on de/anti-icing fluid holdover times. We have been conducting research with de/anti-icing fluids since the early 1990s and are the only company in the world to conduct official holdover time testing; it is our research and analysis which determines the data that populates the holdover timetables.

We also draft and manage the Transport Canada and FAA Holdover Time documents. Basically, we know HOT data better than anyone else and are uniquely qualified to provide this information in an app.


How widely used is this app?

The APS Holdover Times app is currently being used by multiple major airlines in North America. Over 20,000 pilots used the app in the winter of 2014-15 and that number is expected to increase significantly for winter 2015-16. We have users across the globe from Europe to Asia to Australia. Feedback on our app has been extremely positive.


Has the app been certified / approved by authorities?

Neither Transport Canada nor the FAA certifies or approves holdover time apps. However, they do have (different) processes in place to authorize their use. Contact us ( ) for more information and supporting documentation.


Do I need an internet connection to use the app?

No internet connection is required to use this app as the app stores all needed data on your device. It is recommended you connect your device to the internet periodically to check for app updates.


How can I be sure the HOT Calculator will return accurate information?

APS undertakes an extensive process to verify all data in the app. This process includes a manual verification of every possible combination of parameters used by the HOT calculator to verify the correct holdover time, notes and cautions are provided for those specific parameters.

The verification process is documented both electronically and in hard copy and can be made available upon request by pertinent authorities.


How does the holdover time clock work?

The clock can be started once a holdover time is generated. Touch the green "start" button to start the clock. Touch the red "reset" button to reset the clock at any time. (Note: As per operational guidelines, you can't pause the holdover time clock once it has been started).

Once the clock is started, the status bar and traffic light graphics alert you to the status of your holdover time. The traffic light will be green until the lower holdover time in the holdover time range is reached, then turn yellow until the longest time in the holdover time range is reached when it will turn red and flash.

A pop-up warning message will be displayed when the longest time has been reached (this message will be displayed even if another app is being used).


Why do I have to purchase a new app every winter?

We create a new app each year to publish the latest HOT information authorities publish for each winter. We do it this way rather than releasing an update as we need to cover the costs of incorporating the new data.

This includes updating the very large database and the several hundred PDFs that power the app. We also need to check that every single number provided by the app (plus the associated notes, cautions, and PDFs) is correct. This is not only critical for safety, but is also a requirement of the related Transport Canada Advisory Circular - AC 700-030.

Charging annually for our app allows us to continue supporting the app each year and ensures our app, unlike others on the market, has complete and fully accurate data.


Can I get a customized version of the Holdover Times App to meet the specific needs of my airline/operation?

We create customized versions of our app to meet the specific requirements of individual airlines and operators. Customization can include inclusion or exclusion of specific authorities, fluids, holdover times, guidance materials and app features. If you're interested in customization, contact us at


Do you offer training?

Holdover Times is an easy to use, intuitive app which requires minimal training. We offer a How to Use document within the app which guides users through the functionality of the app. Customized training modules are available for customized apps.


Is this app available for Android or Windows-based devices?

This app is currently only available for iOS based devices. Current market demand has been strong for iOS technology so our development has focused on the iOS operating system. Developing Android and/or Windows-based versions is something being strongly considered for future, should market demand increase.


How do I know the information in the app has not expired?

The authorities who publish the data included in this app do not include expiry dates when they publish their data. Therefore, the data has no official expiry date. The data only becomes obsolete when a newer version is published. Newer versions are published annually, for each winter season, typically in late summer / early fall.

We create and publish a new app every fall to provide the new winter’s published information. If an update to a publication is released mid-season, we update the current winter’s app accordingly and release a free update. To ensure a previous winter’s app (and its obsolete data) is not used, we have programmed our app to stop working on October 15th of the year following its applicable winter (i.e. the 2016-17 app will stop working on October 15, 2017).


Have more questions?

If your question isn’t answered here, please contact us at