E-commerce companies have proved endlessly creative when it comes to last-mile deliveries, using everything from conventional parcel delivery services to Uber contractors to bicycle and foot couriers. Some are even experimenting with drones and self-driving parcel delivery robots.

Apparently, that array is not diverse enough for megaretailer Amazon.com Inc. Amazon recently filed patents for delivery systems involving flying warehouses and networks of underground tunnels.

In its patent filing for the flying warehouse, Amazon describes a system that uses blimplike airborne fulfillment centers (AFCs) outfitted with drones to drop off orders. To make deliveries, an airship would navigate to the customer's location, where it would hover about 45,000 feet off the ground and dispatch an unmanned aerial vehicle (drone) to deliver the items. As for how the company would resupply the AFCs, Amazon would dispatch smaller airborne "shuttles" to replenish the flying warehouse with inventory, drones, supplies, fuel, and—yes—human workers.

Amazon's other recent patent award was for a tunnel delivery network that avoids congested surface roads. Rather than using traditional highway networks, the e-tailer would whisk parcels and containers to their destinations via subterranean conveyors or rails. Items would ride on standard conveyor belts for horizontal travel underground and then return to the surface via ramps and spiral conveyors.

The patent filing contains no mention of whether Amazon will employ armies of rabbits to dig the underground warrens.