What does the runway controller do to prevent a landing?

The runway controller plays a critical role in ensuring the safety of aircraft during landings and takeoffs at an airport. To prevent a landing, the controller uses specific visual signals to communicate with pilots. A steady red lamp is one of the most universally recognized signals indicating to pilots that the runway is not safe for landing. When the steady red light is displayed, it instructs pilots to go around and not to attempt to touch down on the runway, as it may be occupied or unsafe for landing.

In contrast, a steady green lamp indicates that the runway is clear and safe for landing, while a flashing yellow light typically serves as a cautionary signal rather than an outright stop command. The absence of a specific signal would imply that no action to prevent a landing is being communicated, which is not the function of the runway controller in this context. Thus, the use of a steady red lamp effectively communicates that a landing should not be attempted, reinforcing the controller's authority and ensuring safety at the airport.