What is the general criteria for an airline to pick an alternate?

• A. the number of GNSS approaches, along with the TAF forecast
• B. the number of runways, along with NOTAMS
• C. the number of precision IFR approaches, alone with a TAF
• D. the wind direction, along with a GFA forecast

Answer: (C)

When choosing an alternate, you want to ensure you can actually land there if needed. The best way to ensure that is that the alternate has instrument landing capability, specifically precision IFR approaches, and that the forecast weather supports landing at that airport.

Having a higher number of precision IFR approaches means there are routes with the lowest landing minimums available at the alternate. This increases the chance you can complete a safe landing even in poorer visibility or lower ceilings, which is exactly what you need when you’re diverting. Pairing that with a TAF forecast provides the weather outlook for the alternate during the time you’d be arriving, letting you verify that the forecast ceilings and visibility will meet those minimums.

The other options don’t tie together approach capability and forecasted weather in a way that reliably supports a diversion decision. GNSS approaches may or may not provide the necessary precision minima; NOTAMs alert you to temporary problems but don’t guarantee acceptable landing conditions; wind direction alone doesn’t indicate whether you can land, and a general GFA forecast isn’t specific to the airport’s published instrument minimums.