Flying in winter conditions comes with unique challenges, and one of the most critical safety factors is understanding and applying Holdover Times (HOT). For pilots, knowing exactly how long de-icing or anti-icing fluid will remain effective is essential to ensure a safe departure.
In this article, we explain what holdover times are, why they matter, how they are calculated according to the latest FAA guidance, and how Wilco makes this process easier by integrating GPS and real-time weather data.
What are Holdover Times?
Holdover Time (HOT) is the estimated time that de-icing or anti-icing fluid will prevent the accumulation of frost, ice, or snow on an aircraft’s critical surfaces. In simple terms, it is the “window of protection” that starts the moment de-icing is complete and ends when the fluid can no longer protect the aircraft.
This time depends on many factors:
Type and concentration of fluid used.
Outside air temperature.
Type and intensity of precipitation (snow, freezing rain, sleet, ice pellets).
Wind conditions.
Weather trends based on the latest METAR.
Exceeding the HOT is a serious safety risk, as it means the fluid may no longer prevent contamination of the aircraft surfaces.
FAA Guidance on Holdover Times
The Federal Aviation Administration (FAA) publishes updated Holdover Time Guidelines every winter. These documents include tables that show the range of HOT values depending on fluid type, dilution, temperature, and weather conditions. Pilots are required to use the latest version to ensure accuracy.
For example:
Type I fluids provide short HOT values and are used primarily for de-icing just before departure.
Type II, III, and IV fluids provide longer HOT values, making them suitable for anti-icing protection in active precipitation.
The FAA guidance emphasizes that holdover times are ranges (for example, 20–45 minutes). The actual protection time can be shorter in heavy precipitation, or longer under lighter conditions. Pilots must always apply operational judgment and continuous observation of aircraft surfaces.
Challenges for pilots
Traditionally, calculating HOT required cross-checking FAA tables, knowing the exact type and concentration of fluid used, and manually aligning this with current METAR or ATIS reports. In fast-changing weather conditions, this process can be stressful and prone to error.
Pilots often face problems such as:
Outdated weather information.
Uncertainty about fluid type and concentration.
Misinterpretation of holdover charts.
Time pressure during winter operations.
How Wilco simplifies Holdover Time management
Wilco integrates the latest FAA Holdover Time Guidance into its platform, making HOT calculations simple, accurate, and reliable:
Automatic GPS-based weather updates – Wilco fetches the most recent METAR for your location, ensuring you always use the latest conditions.
Integrated HOT calculator – based on the most recent FAA guidance, Wilco calculates holdover times tailored to the type and concentration of de-icing/anti-icing fluid used.
Real-time decision support – a clear progress bar shows exactly how much time you have left before HOT expires, so you can monitor protection at a glance.
With Wilco, you no longer need to flip through tables or worry about whether your weather data is outdated. The system combines GPS and live weather feeds with FAA’s official guidance to give you precise, actionable holdover times.
Why it matters
Holdover times are a critical part of winter flight safety. Using outdated tables, incorrect weather, or rough estimates can compromise safety margins. By automating HOT calculations and displaying them with a simple progress bar, Wilco helps pilots:
Fly with greater confidence in winter operations.
Save time during pre-departure preparation.
Reduce the risk of human error.
Stay visually aware of the HOT countdown without distraction.
Conclusion
Winter flying requires precision, and understanding holdover times is at the heart of safe operations in snow and ice. With Wilco, pilots get the most up-to-date FAA holdover guidance, GPS-based weather integration, and automatic HOT calculation in one professional tool.
No more guessing, no more outdated data – just reliable protection windows, displayed clearly in a progress bar.
Wilco turns one of the most stressful parts of winter flying into a simple, intuitive process, giving you more time to focus on what really matters: flying safely.