Which aspect of ATC light gun signals allows them to be universally understood?

The correct answer emphasizes that light gun signals in air traffic control (ATC) follow international standards, which is key to their universal understanding among pilots and air traffic controllers globally. These standards are established by the International Civil Aviation Organization (ICAO) and ensure that light gun signals convey the same meaning regardless of the country or specific ATC procedures in use. This consistency is vital in ensuring safety and clarity, especially in situations where verbal communication might not be possible, such as when an aircraft is not equipped with radio communication capabilities.

While color-coding is an important characteristic of the signals, it is the adherence to international standards that guarantees their universal comprehension among international aviation personnel. The codes and meanings associated with each color of the light gun signals (such as green for cleared to land or takeoff, red for stop, etc.) are standardized across countries, which helps prevent misunderstandings.