Amazon recently received approval from the Federal Aviation Administration to operate unmanned air vehicles (UAVs) for RnD purposes. With this approval, Amazon may start testing the UAVs for deliveries at certain authorized locations.
Here, we have an Amazon patent US9305280B1 filed way back in 2014 that describes an 'Airborne fulfillment center' that uses UAVs to deliver packages to customers. The Airborne fulfillment center is envisioned, in some drawings, a flying warehouse that stays afloat with hot air or helium.
In the above Figure, UAVs (312) can deploy from the flying warehouse (302) to deliver packages to customers. Smaller shuttles (350) can fly up to the flying warehouse to add inventory to it and otherwise replenish the airship so that it can stay up in the air.