When discussing the requirement for an alternate airport, which rule is typically referenced?

The requirement for an alternate airport is commonly discussed in the context of the 1-2-3 rule. This rule provides a simple guideline for pilots determining when an alternate airport is necessary based on the weather conditions at the destination and anticipated arrival times.

Specifically, the 1-2-3 rule states that if, at the estimated time of arrival, the ceiling is less than 2,000 feet and/or visibility is less than 3 statute miles at the destination airport, an alternate airport is required. The rule serves as a safety measure to ensure that a pilot has a plan to divert to another airport in case of poor weather conditions at the intended destination.

Having this guideline helps pilots make informed decisions about flight planning and enhances safety during operations, ensuring they comply with regulations pertaining to alternate airports.