What does the Fasten Seatbelt Sign indicate to passengers?

The Fasten Seatbelt Sign indicates that passengers should remain seated with their seatbelts fastened. This is a crucial safety measure, as it helps ensure that passengers are securely strapped in during turbulent conditions or when the aircraft encounters unexpected movements. Keeping the seatbelt fastened is vital for individual safety, reducing the risk of injury.

While the other options may seem relevant to different flight scenarios, they do not directly relate to the specific purpose of the Fasten Seatbelt Sign. For instance, preparing for landing is a distinct procedure that may not happen simultaneously with the sign being illuminated. Similarly, the sign does not indicate that it is safe to move about the cabin or that flight attendants are serving meals; in fact, during those times, passengers are often advised to remain seated. Thus, the most accurate interpretation of the sign's purpose is that passengers should remain seated with their seatbelts fastened at all times when the sign is illuminated.