According to the second Nav Aid rule, how many operational navigational facilities are required for the procedure?

The second Nav Aid rule stipulates that for a procedure to be considered operational, there must be at least two navigational facilities in place. This requirement ensures redundancy and enhances the reliability of navigation during flight operations. Using multiple navigational aids allows pilots to cross-check their position and confirm their intended flight path, which is crucial for maintaining safety and efficiency, particularly in complex flight environments. By having at least two navigational facilities, pilots can navigate more effectively, mitigating the risk of errors arising from reliance on a single source of information. This principle reflects the broader emphasis on safety and operational integrity in aviation practices.