Describe the role of an air traffic controller.

The role of an air traffic controller is central to maintaining the safety and efficiency of air travel. This position involves directing aircraft both in the air and on the ground, ensuring that safe distances are consistently maintained between them, which is crucial for preventing collisions. Controllers provide instructions regarding altitude, speed, and route changes to pilots, effectively facilitating smooth transitions during takeoff, cruising, and landing phases.

The other choices do not align with the responsibilities of an air traffic controller. Managing passenger boarding is primarily the responsibility of airline staff, while conducting maintenance checks involves qualified mechanics and engineers. Providing in-flight entertainment is irrelevant to air traffic control duties, as it pertains to airline services focused on passenger experience. Thus, the essential task of maintaining safe distances between aircraft during all flight stages reinforces the critical function of air traffic control in ensuring a safe airspace environment.