However, Amazon is looking at going beyond that to potentially using a mobile drone port to provide disaster relief supplies following an incident. Check out Mobile Hubs for Drone Delivery.It is a rail option in the diagram, but it could also be performed from semi-truck trailers. In their patent application, Amazon put it this way; "When a particular area is experiencing a lengthy spell of good weather, a national championship by a local sports team, a natural disaster, or other unique event, demand for items within the area ..."
Don't limit your thinking about the use of drones; Amazon is not.