Where must the NO1 remain when the pilot has vacated their seat in the FD?

The correct answer is that the NO1, which refers to the first officer or designated crew member, must remain in the forward galley when the pilot has vacated their seat in the flight deck (FD). This position is crucial for ensuring safety and security during times when the pilot is temporarily away from their controls, primarily to maintain constant monitoring of the cabin and cabin crew operations.

By staying in the forward galley, the NO1 is strategically placed to quickly respond to any issues that may arise in the cabin, while also maintaining communication with the pilot, if necessary. This position allows them to oversee the crew and passengers effectively, ensuring they can address any immediate concerns related to safety or procedural matters.

In contrast, the other options do not suitably ensure the required level of oversight or readiness. Being at the back of the cabin or in the passenger area removes the NO1 from immediate access to the flight deck and the ability to act swiftly if any unusual situation arises. Remaining at the FD door may provide a sense of proximity to the flight deck but lacks the oversight advantage and preparedness that being in the forward galley offers. Therefore, the forward galley position optimally balances accessibility to the flight deck and accountability for cabin safety.