What is the purpose of having a clearway associated with a runway?

The correct answer highlights the purpose of having a clearway associated with a runway, which is primarily to increase the length of the takeoff distance available for an aircraft. A clearway is an area beyond the end of the runway that is kept free of obstacles and is suitable for an aircraft to continue its climb if it experiences an initial failure shortly after takeoff.

By extending the available distance for takeoff and allowing the aircraft to clear obstacles safely, the clearway enhances the overall safety of operations, especially for larger aircraft that may require more takeoff distance. This provision is crucial in ensuring that the aircraft can achieve necessary climb performance and avoid any potential hazards that lie ahead.

In contrast, the other options do not accurately reflect the defined role of a clearway in airport operations. While a clearway contributes to takeoff safety, it does not function as a parking area for waiting aircraft, ensure safe landings for all aircraft types, or serve as an alternate runway. Each of these roles involves different areas and considerations within airport management and aircraft operations.