A Visual Approach Slope Indicator (VASI) is a lighting system used at airports to help pilots maintain the correct glide path during landing. It consists of a series of lights that indicate whether the aircraft is above, below, or on the ideal approach slope. The lights typically change color, providing immediate visual feedback to the pilot. The VASI system enhances safety by reducing the risk of landing accidents caused by improper approach angles. It is commonly found near runways and is an essential tool for both commercial and private aviation, ensuring that pilots can land safely in various weather conditions.