Accessing and calculating holdover times has never been easier. 

Holdover Times
Quicker and safer holdover time calculations easily accessible in an iOS app.
Trusted Worldwide
Ten major airlines and over 45,000 pilots in 30 countries now use the APS Holdover Times App.
Extensive experience and exhaustive data verification warranty the accuracy of every holdover time provided.

Key Features
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HOT Calculator

Calculate the holdover time for current conditions by entering the applicable weather and fluid information. The appropriate holdover time will be provided, along with all related notes and cautions and the applicable holdover time table PDF.

Use the “HOT Clock” and related graphics to keep track of the status of your holdover time: progress wheel indicates status of HOT; alerts are provided when lower (optional) and upper HOTs are reached.

METAR (New!)

Enable METAR functionality to access METAR reports through the HOT Calculator. Make sure to tap Refresh to get the latest report (METAR does not update automatically) and tap the airport name to find a report for a different location.

PDF Viewer

Use the PDF viewer to access the Transport Canada and FAA 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.

Related guidance documents for each authority are also provided and easily accessible.

Event Log (New!)

Each time you start the HOT Clock an event will be created with all pertinent event details. Access this data in the More tab. Events can be exported via email either individually or in aggregate. They can also be deleted. Note: Event log data is stored locally on your device.

Changeable Settings

Customize your authority, HOT table type (standard or adjusted), HOT alerts (lower, upper, both) and time zone (local or UTC). Enable or disable METAR functionality.

event log

App Customization

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.

We can also incorporate your company’s guidance materials – including deicing checklists – either as PDFs or integrated into app functionality.

Learn how a customized app can help your business operate more safely and efficiently in winter conditions.

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Frequently Asked Questions (FAQs)

If your question isn’t answered here, please contact us at apps@apsaviation.ca.



Do I need an internet connection to use the app?

No internet connection is required to obtain HOT data from the app, as this data is stored locally on your device. An Internet connection is only required to access METAR reports. We recommend connecting your device to the internet periodically to check for app updates.

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

This app is currently only available for iOS-based devices.

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

Authorities publish new HOT information every winter. We correspondingly create a new app to provide this new HOT information to users. This process includes updating the extensive database and PDFs that power the app and carrying out a thorough verification of all changes (this verification is not only critical for safety, but is also a requirement of the related Transport Canada Advisory Circular). Charging for a new app allows us to carry out this work annually.

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.



What qualifies APS Aviation to create this app?

We are the world’s leading experts on de/anti-icing fluid holdover times (HOTs). 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 time tables. We also draft and manage the Transport Canada and FAA Holdover Time documents. This knowledge uniquely qualifies us to provide HOT information in an app.

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. Operators in both jurisdictions have gone through these processes and are currently authorized to use our app. Contact us for more information and support.

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

APS undertakes an extensive process to verify all data in this app. This process includes a manual verification of every possible combination of parameters used by the HOT calculator to verify that the correct holdover or allowance 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 do I know the information in the app has not expired?

Authorities do not include expiry dates when they publish holdover time data. Therefore, the data has no official expiry date. It only becomes obsolete when a newer version is issued. New versions are published annually, for each winter season, typically in late summer / early fall. They are also sometimes published mid-season. We update the app each time new HOT data becomes available. Because we know holdover time data is published for each winter season, if your app does not have the latest update installed by October 15th, you will receive a message reminding you to update the app. The HOT Calculator and PDF Viewers will not be available until the update is installed. This ensures the app is not being used with the previous winter's data.


Why is the HOT Calculator giving me the message "No Holdover Times Exist"?

Holdover times do not exist in all conditions. When you get this message, an explanation is provided in the line below. For example: you’ve chosen a precipitation type for which holdover times or allowance times are not provided (i.e. heavy snow, hail) or have chosen a fluid type that can’t be used in the conditions selected (e.g. Type I fluid in Ice Pellets).

Why am I not getting alerts from the HOT Calculator?

If you are not getting alerts from the HOT Calculator, check your device settings:

  • Open the settings app on your iPad/iPhone, scroll down on the left menu, and tap “2019-20 HOTs”
  • On the right side of the screen, tap “Notifications”
  • Ensure that “Allow Notifications” is on
  • We recommend enabling banners and setting the Banner Style to “Persistent”
  • We also recommend enabling alerts on the lock screen and enabling alert sounds and badges

How are Lowest Operational Use Temperatures (LOUTs) incorporated into the HOT Calculator?

The LOUTs published by Transport Canada and the FAA for Type II, III and IV fluids are incorporated into the HOT Calculator. When one of these fluids is selected and a temperature below the fluid’s LOUT is entered, no holdover time will be provided. If LOUTs are not available for a specific fluid, a caution note is provided accordingly.

About Us

APS Aviation Inc. is an engineering consulting firm based in Montreal, Canada. We work predominantly in the aviation industry and specialize in winter operations. We have been responsible for developing and managing the holdover time table data on behalf of Transport Canada and the FAA for the last two decades. We are a member of the RHEA Group.

APS Holdover Times App Terms of Use and Privacy Policy