IFR Alternate Aerodrome Requirements in Canada

Alternate aerodrome planning is one of the most number-heavy topics on the INRAT. There are specific weather thresholds for when you need an alternate, specific minimums for what qualifies as one, and fuel requirements on top of that. Get the numbers wrong on the exam and you'll lose marks even if your reasoning is right.

When do you need an alternate?

You need a filed alternate when the forecast weather at your destination is below certain thresholds for the period from one hour before to one hour after your estimated time of arrival.

Both the ceiling and visibility must be at or above the threshold to avoid needing an alternate. If either is below — even if the other is fine — you file an alternate.

What qualifies as an alternate?

Not every airport can serve as your alternate. The forecast weather at the alternate must meet its own set of minimums at your ETA:

These are lower than the destination thresholds because by the time you divert, you're already airborne and committed. The alternate just needs to be usable — not comfortable.

Satellite-based approaches as alternates

RNAV (GNSS) approaches can be used to qualify an alternate, but with a restriction: you cannot use the same navigation system for both your destination approach and your alternate if a failure of that system would leave you without any approach at either location. In practice, if your destination is RNAV and your alternate is also RNAV-only, you need to verify that a GPS outage wouldn't strand you at both simultaneously.

Aerodromes served only by GFA

Some remote Canadian aerodromes don't have TAF forecasts — they're covered only by the Graphic Area Forecast (GFA). An aerodrome served only by GFA can qualify as an alternate, but the forecast weather must meet the standard alternate minimums. The exam will sometimes specify a GFA-only aerodrome and ask whether it qualifies — the answer depends on the forecast, not the forecast source.

Alternate minima in Canada

The term alternate minima refers to the minimum forecast weather conditions that an aerodrome must have to qualify as a legal IFR alternate. In Canada, these are set out in the CARs and depend on the type of approach available at the alternate aerodrome.

The alternate minima for Canadian IFR flight planning are:

These alternate minima are lower than your destination thresholds because at the point of diversion you're already airborne — the alternate just needs to be workable. The exam uses the phrase "alternate minima" directly in some questions, so it's worth knowing the term, not just the numbers.

Enroute alternates

For long over-water or remote flights, Transport Canada may require an enroute alternate — an aerodrome you could divert to mid-flight if a problem develops before you reach your destination. Enroute alternates are separate from your filed destination alternate and are typically required when flying beyond gliding distance of land or in ETOPS operations. The INRAT doesn't test enroute alternates deeply, but knowing the concept distinguishes it from a standard filed alternate.

Fuel requirements with an alternate

When an alternate is required, your fuel planning must include: fuel to destination, plus fuel to the alternate, plus 45 minutes reserve at normal cruise (for piston aircraft). Turbine aircraft have different reserve requirements. The INRAT will occasionally give you a fuel scenario and ask whether the planned fuel load is sufficient — knowing the structure of the requirement matters as much as the numbers. The fuel rules fit into a larger picture of what goes on an IFR flight plan in Canada, including when one is required, required fields, and how to close it after landing.

Quick reference — all the numbers