At what altitude can recognition lights be turned off?

• A. 10,000 feet
• B. 14,000 feet
• C. 18,000 feet
• D. 21,000 feet

Answer: (C)

Recognition lights exist to help pilots spot tall obstacles, especially in low visibility or at night. A regulation sets a height threshold where those lights may be turned off because the risk profile changes at higher altitudes. Once the top of the obstruction reaches about 18,000 feet, most en route traffic operates at different flight levels, and lighting the obstacle no longer provides the same safety benefit relative to the energy and maintenance cost. So turning off recognition lights above 18,000 feet is permitted, while they remain on for lower elevations to keep the obstacle visible to aircraft that might encounter it at lower levels. Always follow the specific regulatory guidance for your region, but the 18,000-foot mark is the commonly cited threshold.