What could be a consequence of improperly storing items under the lavatory sinks?

Improperly storing items under the lavatory sinks can lead to a fire hazard. This area often contains various materials, including cleaning supplies and other flammable items that do not belong there. If these materials are not stored correctly and are exposed to heat sources or generated sparks, they could ignite, posing a significant risk to the safety of the aircraft, crew, and passengers.

In contrast, while diminished service efficiency, higher cleaning costs, or passenger comfort might be impacted by poor storage practices, the most immediate and critical concern is the potential for a fire, which can have dire consequences. Proper storage of materials not only ensures safety but also complies with regulatory standards regarding hazardous materials on board.