The Aeronautical Information Manual suggests turning on landing lights below 10,000 feet, day or night, and especially when operating in what condition?

• A. Clear weather with good visibility
• B. Reduced visibility
• C. Stormy weather with lightning
• D. Increasing altitude toward 20,000 feet

Answer: (B)

The idea here is that turning on landing lights below 10,000 feet makes your glider more conspicuous to other pilots, which is especially important when visibility is limited. When visibility is reduced—due to haze, fog, precipitation, or low light—aircraft can blend into the background more easily, so the lights help others see you sooner and judge where you are and how fast you’re moving. That extra visibility reduces the chance of a mid-air encounter. In clear weather with good visibility, the need isn’t as urgent, and the other options don’t hinge on visibility in the same way. The reference to reduced visibility is why that choice is the best.