For landing minimums, what is the additional requirement under the Nav Aid rule for airports with at least one operational navigational facility?

In the context of landing minimums under the Nav Aid rule for airports equipped with at least one operational navigational facility, the requirement is to add 1 statute mile to the standard landing minimum. This rule is put in place to ensure that pilots maintain adequate visibility and navigational assistance during the approach and landing phases, which are critical for safety.

The rationale behind this addition is that while the operational navigational facility provides important guidance, an extra margin of visibility is necessary to compensate for any potential limitations in the aid or unforeseen weather conditions. This requirement emphasizes the importance of safety, ensuring that pilots have a greater than minimum assurance of being able to see the runway and navigate successfully to land.

Other options propose different additional distances, but the specific requirement set by the Nav Aid rule is to add 1 statute mile, making this the correct answer.