The number one choice in the industry for winter flight safety

Brought to you by the same research team behind the development of winter flight holdover times, this is the number one choice  in the aviation industry for enhancing safety in inclement winter weather conditions.

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Quicker holdover time calculations easily accessible in an iOS app designed to improve winter flight safety.

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Over 290,000 pilot downloads since 2012, used in more than 30 countries and by many major airlines.

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Extensive experience and exhaustive data verification warrant the accuracy of every holdover time provided.

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We can customize the app for your airline’s requirements and potentially integrate checklists to help improve safety.

Be fully prepared for the 2023-24 winter operations

Ready for download on the app store or build your own app!

APS Aviation HOT App 2023 home screen and timer screen


Download the APS Aviation Holdover Times app

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APS Aviation HOT App 2023 calculator screen

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.

Degree-Specific HOTs

Enable DSHOTs functionality to access the degree specific holdover times in Snow, Snow Grains and Snow Pellets, through the HOT Calculator.


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.

Mixed icing conditions

New mixed icing precipitation conditions as included in the Transport Canada and Federal Aviation Administration HOT guidelines.

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

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 degree-specific HOTs, and METAR functionality.

Choose the colour scheme for the app (dark and light modes) for better visibility in difference lighting conditions.

APS Aviation HOT App 2023

Download now on the app store

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Build your own app

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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“The APS HOT app is an outstanding tool in its own right, but the customization that the APS team has done for us has aligned the app even more closely with our requirements. The app will definitely enhance our airline’s safety during inclement winter weather conditions and marks a major step forward for us from using traditional paper tables.”
Giulio Marciano, Team Lead, iAero Airways

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Frequently Asked Questions (FAQs)

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.

APS is the only company in the world to conduct official holdover time testing; it is our research and analysis that 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 or 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.

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

Holdover times do not exist in all conditions. When this message is displayed, an explanation is provided in the line(s) below. For example: a precipitation type for which holdover times or allowance times are not provided has been selected (i.e. heavy snow, hail) or a fluid type has been chosen that cannot 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 notifications settings:

  • Open the Settings app on your device, scroll down on the left menu, and tap “2022-23 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.

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 published. New versions are published annually, for each winter season, typically in late summer or early autumn/fall. We create and publish a new app every autumn/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 providing HOT information on 1 November of the year following its applicable winter (i.e. the 2022-23 app will stop working on 1 November 2023).

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.

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 that requires minimal training. We offer a How to Use document within the app that guides users through the functionality of the app. Customized training modules are available for customized apps.

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.

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Download the app directly from the app store or contact us to create your own app.

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APS Holdover Times App Terms of Use and Privacy Policy