What is the required visibility to select two alternates if the ceiling forecast within one hour of ETA is less than the stipulated minimums?

To effectively select two alternate airports when the forecasted ceiling is below the stipulated minimums, the required visibility is indeed 5 kilometers. This requirement is rooted in aviation regulations that aim to ensure safe operations under conditions where the primary destination may not meet the necessary weather criteria for a safe landing.

The rationale behind this specific visibility requirement is to provide pilots with adequate options in case a diversion becomes necessary. By establishing a minimum visibility of 5 kilometers, it allows the pilots not only to assess the conditions at the alternate airports but also ensures that the flight can safely land if rerouted.

Choosing an alternate airport is a critical aspect of flight planning, as it addresses uncertainties in weather conditions, and it emphasizes the importance of operational safety by ensuring that alternatives are available in poor weather scenarios. Thus, the adherence to the stipulated minimum helps maintain standards of safety and navigational precision in aviation operations.