What is the purpose of a white box preceding a runway?

A white box preceding a runway serves as a blast pad. The primary purpose of a blast pad is to protect the runway from the erosive effects of jet blast during takeoff and landing operations. This area helps to reduce the impact of the powerful jet blasts generated by aircraft engines, which can lead to damage and degradation of the runway surface over time. By including a blast pad in runway design, airports enhance safety and prolong the lifespan of the runway infrastructure.

While visual aids and runway designations also play important roles in airport operations, their functions are distinct from that of a blast pad. A white box is not primarily meant for safety zones or simply as a visual aid; rather, it is specifically designed to mitigate the effects of jet blast and ensure safer operations around the runway area.