In which zones of the runway are repairs required to be flush?

Repairs in the critical zones of a runway must be flush to ensure the safety and efficiency of aircraft operations. The critical zone refers to areas of the runway that are crucial for takeoff and landing, where any irregularities can significantly impact aircraft performance. Having repairs flush in these zones minimizes the risk of damage to landing gear and improves aerodynamics by providing a smooth surface. This attention to detail is essential for maintaining the operational integrity of the runway, as even small irregularities can lead to increased wear and tear on aircraft, as well as potential safety hazards during critical flight phases.