What does a red over red indication on a VASI indicate?

A red over red indication on a VASI (Visual Approach Slope Indicator) signifies that the aircraft is below the proper glide path for landing. The VASI system helps pilots maintain the correct descent angle by displaying different colors based on their vertical position relative to the glide path. When the lights show red over red, it serves as a warning to the pilot, indicating that immediate corrective action is needed to climb and reach the proper glide slope for a safe landing. The VASI is designed to aid pilots in visual approaches by providing a clear visual cue of their altitude in relation to the runway approach slope, which is typically set around a 3-degree angle.