Can the lavatory door be locked from the outside?

The lavatory door can indeed be locked from the outside in certain situations, specifically for proper cabin security and privacy. This feature is typically designed to be used in circumstances where it may be necessary to control access to the lavatory, such as during specific operational protocols or to ensure safety.

When a door is lockable from the outside, it allows crew members to manage access effectively, especially in case of emergencies or when monitoring passenger usage in high-traffic situations. The ability to lock the lavatory door from the outside is an operational safety feature that enhances the cabin crew's ability to oversee the cabin environment.

In contrast, the concept of the door not being lockable from the outside, only being lockable in emergencies, or being lockable only when in the air reflects limitations that do not align with the operational capabilities of typical aircraft lavatory systems. These options suggest scenarios that would hinder the crew's ability to ensure passenger safety and fluid cabin operations.