What is the general requirement for safety belt use for all passengers?

The requirement for safety belt use for all passengers is to ensure their safety during critical phases of flight. Passengers must be secured during taxi, takeoff, and landings, as these are the times when the aircraft is most vulnerable to sudden changes in speed or altitude, which can lead to accidents or injuries.

During taxi, the aircraft is still maneuvering on the ground, and unexpected stops or collisions can occur. During takeoff and landing, which are phases of flight that involve significant changes in both speed and altitude, the likelihood of turbulence or other unexpected events increases. Having seat belts secured during these times minimizes the risk of injury from sudden movements of the aircraft.

The other options suggest scenarios that compromise passenger safety. Securing belts only during takeoff or landing ignores the risks present during taxi. Claiming that the use of seat belts is not mandatory undermines the established safety regulations set forth by aviation authorities. Finally, limiting seat belt use to only during landings overlooks the necessary precautions needed during takeoff and taxi. Thus, the correct choice encompasses the most comprehensive and safety-conscious approach to seat belt use.