Which factor is NOT directly related to the '1-2-3 rule'?

The '1-2-3 rule' is particularly relevant to flight planning and approach decisions, specifically focusing on weather requirements for landing. This rule helps pilots determine if an approach can be made based on time constraints, ceiling, and visibility. The factors of time before and after the estimated time of arrival, ceiling requirements, and visibility conditions all directly relate to whether the approach and landing can safely proceed.

Time before and after ETA helps pilots assess if they can afford delays due to weather conditions, while ceiling requirements and visibility conditions are essential to ensure safe landing capability under regulated standards.

In contrast, aircraft weight does not directly influence the '1-2-3 rule.' Aircraft weight pertains to performance parameters like takeoff, climb rate, fuel consumption, and landing distance, but it does not factor into the weather-related conditions prescribed by the '1-2-3 rule.' Therefore, it's not a consideration within the context of this specific rule.