What can be used as a protective barrier for the flight deck if a secondary barrier is not available?

Using a full-size galley cart as a protective barrier for the flight deck is effective due to its sturdy construction and mobility. In instances where a secondary barrier is needed, the galley cart can be positioned in such a way to obstruct the entrance to the flight deck, providing an additional layer of security.

The galley cart is designed to withstand significant weight and impact, which makes it more reliable as a physical barrier compared to other options. For example, while seat cushions might provide some cushioning, they lack the structural integrity necessary to act as a formidable barrier. Similarly, cabin crew luggage is typically not designed for this purpose and does not offer the same level of protection. The emergency exit door is also not a practical obstacle for creating a barrier between the cabin and the flight deck since it serves a different function and is generally not movable. Thus, the full-size galley cart emerges as the most suitable alternative when a secondary barrier is not readily available.