Shoulder harnesses must be fastened during which phases?

• A. Takeoff and landing
• B. Cruise only
• C. During turbulence
• D. Only when the seat belt sign is on

Answer: (A)

The essential idea is that the shoulder harness provides restraint for the upper body when the airplane is most likely to experience sudden, high loads. Takeoff and landing are the phases with the greatest potential for rapid deceleration or abrupt movement, so fastening the shoulder harness then helps prevent injuries to the head, neck, and torso and keeps you properly seated.

Cruise flight doesn’t carry the same level of abrupt forces as takeoff or landing, so the rule isn’t focused on that phase. The option about turbulence implies a special timing, but the standard requirement is tied to the critical phases of takeoff and landing, not to turbulence or to the seat belt sign being on.