What must occupants do during all phases of flight, according to safety regulations?

Occupants are required to wear seatbelts and shoulder harnesses during all phases of flight to ensure their safety. This regulation is vital as it helps to restrain individuals in their seats in the event of turbulence, sudden stops, or emergencies, significantly reducing the risk of injury. These safety measures are designed to keep passengers securely fastened in place, minimizing the chances of them being thrown forward or moving around the cabin, which could lead to accidents or injuries.

Maintaining the use of seatbelts and shoulder harnesses throughout the entire flight, including cruising altitude, enhances overall safety by preparing passengers for any unexpected circumstances that may arise. In contrast, the other options either suggest removing restraints or wearing safety gear only during critical flight stages, which are suboptimal practices and do not align with current aviation safety standards.