During which phases must seatbelts be fastened?

The correct answer pertains to the specific phases of flight during which the regulation requires passengers to have their seatbelts fastened for safety reasons. Seatbelts are crucial during critical phases of flight, including take-off and landing, as these are when the aircraft is most vulnerable due to the potential for sudden changes in speed and altitude, or the need for immediate maneuverability.

During taxi, while the aircraft is moving on the ground, the risk of significant turbulence is lower compared to the other phases. However, it is still advisable for passengers to keep their seatbelts fastened during taxiing as a precaution against unexpected stops and starts.

The other phases listed in the options do not emphasize the correct regulatory requirements for seatbelt use. For instance, cruising involves stable flight conditions where the need for fastening seatbelts is relaxed, unless otherwise instructed by the crew, usually due to turbulence. Therefore, understanding when to fasten seatbelts is key to ensuring passenger safety during the most critical moments of flying: take-off, landing, and taxiing.