The Precision Approach Path Indicator (PAPI) is a visual aid used in aviation to assist pilots during the landing phase of flight. It consists of a series of lights positioned beside the runway, which indicate whether the aircraft is on the correct glide path. Typically, the PAPI lights are arranged in a four-light configuration, with red lights indicating that the aircraft is too low and white lights indicating that it is too high. PAPI systems are crucial for ensuring safe landings, especially in low visibility conditions. They help pilots maintain the proper descent angle, which is usually around 3 degrees. This system is often used in conjunction with other navigational aids, such as the Instrument Landing System (ILS), to enhance landing accuracy and safety.