What do the white blocks on either side of the runway center line indicate?

The white blocks on either side of the runway centerline are specifically used to denote the Touchdown Zone. This area is critical for pilots as it marks the preferred point where aircraft should aim to land when approaching a runway. The Touchdown Zone typically extends from the beginning of the runway to a certain distance down the runway (often up to 3,000 feet for larger runways), providing essential visual guidance for landing.

This marking is crucial for helping pilots ascertain their approach and landing techniques while ensuring a safe descent onto the runway. Each block serves to enhance visibility during low-visibility conditions, making it easier for pilots to identify the runway's centerline as they land.

Recognizing runway markings is fundamental for pilots as it affects landing performance and safety. The other options do not specifically describe the function of these white blocks, as they relate more broadly to runway usage or other visual aids that serve a different purpose in the overall landing process.