When should an additional crew member be present in the flight deck?

An additional crew member is required in the flight deck when one crew member leaves the flight deck for any reason. This ensures that there is always a minimum number of qualified personnel present to operate the aircraft safely. The presence of another crew member maintains communication, oversight, and all necessary operational capabilities, thereby minimizing risks associated with a solo flight deck.

While there may be other scenarios where having an additional crew member seems beneficial, such as during taxiing, ATC requirements, or preparing for takeoff, these situations do not have the same critical nature as maintaining the required crew complement when one member departs. Ensuring that there are always two crew members present in the flight deck is a fundamental safety protocol designed to maintain operational integrity and safety at all times.