Under what condition is an alternate airport required for flight planning?

• A. When the destination weather is forecast to be worse than 2000 ft ceiling and 3 statute miles visibility within ETA +/- 1 hour
• B. Whenever the flight is longer than 4 hours
• C. Only when night operations are planned
• D. When the destination has limited ground facilities

Answer: (A)

The key idea here is that planning an alternate airport is driven by the destination’s forecasted weather, not by flight length, time of day, or ground facilities. If the forecasted conditions at the destination are worse than standard landing minimums, you must designate an alternate. The standard threshold used in many planning scenarios is a ceiling of 2000 feet and visibility of 3 statute miles, and this forecast must be within the ETA plus or minus one hour. This window accounts for slight timing differences and ensures you have a viable backup landing if conditions at the destination deteriorate.

So, when the forecasted weather at the destination is worse than those minima within the ETA +/- 1 hour, an alternate airport is required. The other options don’t tie to the weather minimums used for alternate planning: flight duration isn’t the deciding factor, night versus day isn’t the trigger, and lacking ground facilities at the destination doesn’t automatically mandate an alternate.