Choosing an Alternate Aerodrome with a TAF (Canada)

When filing an IFR flight plan in Canada, pilots are required to list an alternate aerodrome—a suitable airport other than the destination, in case landing at the destination becomes impossible.

Photo by Ilyas Dautov on Unsplash

Choosing an alternate involves careful consideration of:

  • Location
  • Available approaches
  • Services offered
  • Weather conditions

If an aerodrome isn’t suitable as a destination, it likely isn't suitable as an alternate either.

Not using a TAF? Learn more about alternate weather requirements using GFAs: Calculating Alternate Weather Requirements for Aerodromes with GFAs.

Regulatory Requirements

The Canadian Aviation Regulations (CARs) state:

CAR 602.122 Except as otherwise authorized by the Minister in an air operator certificate or in a special authorization issued under subsection 604.05(2), no pilot-in-command shall operate an aircraft in IFR flight unless the IFR flight plan or IFR flight itinerary that has been filed for the flight under section 602.73 includes an alternate aerodrome having a landing area suitable for use by that aircraft.

CAR 602.123 No pilot-in-command of an aircraft shall include an alternate aerodrome in an IFR flight plan or IFR flight itinerary unless available weather information indicates that the ceiling and visibility at the alternate aerodrome will, at the expected time of arrival, be at or above the alternate aerodrome weather minima specified in the Canada Air Pilot.

Understanding Approach Types

Precision Approach

Defined in the CARs as: an instrument approach by an aircraft using azimuth and glide path information

Examples: ILS, MLS, PAR.

Note: For the purpose of alternate airports, RNAV/GNSS with vertical guidance is not considered a precision approach. There have been proposals for this to be updated, given the accuracy of many of these approaches. Please refer to the current guidance.

Non-Precision Approach

Defined in the CARs as: an instrument approach by an aircraft using azimuth information

Examples: NDB, VOR, LOC, GNSS (LNAV).

A suitable approach or runway depends on:

  • Wind direction
  • Aircraft capability
  • Runway surface
  • Equipment availability

If an approach isn’t suitable, it can’t be used to calculate alternate minima.

Alternate Weather Minima

Always refer to the current Canada Air Pilot (CAP) for alternate weather minima. The chart below applies only to aerodromes served by Terminal Area Forecasts (TAFs).

Rounding note: Canada rounds weather minima altitudes to the nearest 100 feet.

  • 620 ft → 600 ft
  • 621 ft → 700 ft
Facilities Available at Suitable Alternate Weather Requirements
Two or More Usable Precision Approaches–
each providing straight-in minima to separate suitable runways 		400-1 or 200-½ above the lowest usable HAT and visibility, whichever is greater
One Usable Precision Approach 600-2* or 300-1 above the lowest usable HAT and visibility, whichever is greater
Non-Precision Only Available 800-2* or 300-1 above the lowest usable HAT/HAA and visibility, whichever is greater
No IFR Approach Available Forecast weather must be no lower than 500 feet above a minimum IFR altitude that will permit a VFR approach and landing
For Helicopters
Where instrument approach procedures are available 		Ceiling 200 feet above the minima for the approach to be flown, and visibility at least 1 SM but never less than the minimum visibility for the approach to be flown

*600-2 and 800-2 are considered Standard Alternate Minima

Example 1: One Precision Approach

Alternate: ABC Airport

  • Suitable based on location, services, NOTAMs, and TAF availability
  • Available approaches at ETA:
    • ILS 29: 200 ft, ½ mi (precision)
    • LOC 29: 380 ft, 1 mi
    • LNAV 29: 230 ft, 1 mi
    • VOR 24: 360 ft, 1½ mi
    • NDB 24: 460 ft, 1½ mi

Analysis:

  • Only one usable precision approach
  • Standard minimum: 600-2
  • Chart says:
    • 200 ft HAT + 300 = 500 ft → must use 600 ft
    • ½ mi + 1 = 1½ mi → must use 2 miles

✅ To use ABC as an alternate, the TAF must show at least 600 ft ceiling and 2 SM visibility.

Example 2: Non-Precision Approaches Only

Alternate: DEF Airport

  • Suitable based on location, services, NOTAMs, and TAF availability 
  • Four suitable approaches at ETA:
    • NDB 06: 580 ft, 2 mi
    • LNAV 06: 330 ft, 1½ mi
    • VOR 11: 360 ft, 1½ mi
    • NDB 11: 460 ft, 1½ mi

Analysis:

  • No precision approaches
  • Standard minimum: 800-2
  • Lowest HAT (rounded): 330 → 400 ft + 300 = 700 ft → use 800 ft
  • Visibility: 1½ mi + 1 = 2½ mi → use 2½ miles

✅ DEF requires a TAF showing at least 800 ft ceiling and 2½ SM visibility.

Example 3: Two Precision Approaches (Same Runway Surface)

Alternate: ABC Airport

  • Suitable based on location, services, NOTAMs, and TAF availability  
  • Nine suitable approaches including:
    • ILS 29: 200 ft, ½ mi
    • ILS 11: 200 ft, ½ mi
    • (and more...)

Analysis:

  • While there are two ILS approaches, both land on the same runway surface
  • Therefore, only one usable precision approach counts
  • Use 600-2 standard

✅ Required TAF minimum: 600 ft ceiling, 2 SM visibility

Standard Alternate Minima Sliding Scale

If your required alternate weather is 600-2 or 800-2, the following chart may apply for flexibility:

Standard Alternate Minima If Standard is applicable, then the following minima are also authorized
Ceiling Visibility Ceiling Visibility
600 2 700 1½
800 1
800 2 900 1½
1000 1




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