Final answer:
Cabin signs must be selected ON during critical phases of a flight such as taxi, takeoff, and landing to ensure passenger safety, as part of aviation safety and standard operating procedures.
Step-by-step explanation:
The question refers to a situation in the context of aviation safety and procedures. When it states that both cabin signs must be selected ON during the flight, it commonly aligns with safety protocols that must be followed during critical phases of the flight, such as taxi, takeoff, and landing. This requirement is part of standard operating procedures meant to ensure that passengers are aware of when they should remain seated with their seatbelts fastened.
It is especially critical for cabin signs to be ON indicating that seatbelts should be fastened during taxi, takeoff, and landing phases to minimize the chances of injury due to turbulence or other unforeseen events. These instructions are usually detailed in the airline's flight crew training manual and are part of the safety briefings given to passengers.