An amazon patent filing surfaced on Dec. 28 describing an airborne fulfillment center for the company’s drone delivery system, according to a report by CNBC.

An illustration depicts an airship floating above the city at 45,000 feet from which the drones would fly down to deliver packages. The patent also mentioned possible uses including delivering food and other items to fans at a stadium.

Whether or not the plan is feasible may be up for debate. The logistics of placing a large blimp thousands of feet above a populated area for long periods of time would require regulatory approval, not to mention the fact that Amazon’s drone delivery system is still in its infancy.

Other details of the patent filing include rudimentary plans for midair refueling and restocking from aircraft that could dock with the airship.

The patent was actually approved way back in April 2016 but was not publicized by Amazon at the time. An analyst from CB Insights, which covers the venture capital and angel investment world, posted an image from the filing onto her Twitter account on Dec. 28.

I just unearthed the Death Star of #ecommerce via @cbinsights... AMZN patent for airborne warehouses at 45K ft spitting out delivery drones pic.twitter.com/qEz2ilUtJP

— Zoe Leavitt (@zoe_leavitt) December 28, 2016

The plan itself may never actually come to fruition; many technology companies file for patents as a way of protecting potential ideas. Sometimes the ideas are never followed through on, or they are just a piece of a larger plan that changes over time.

Amazon’s drones have already been tested while being launched from a traditional, ground-based delivery truck. In the U.K. earlier this month, Amazon officially delivered its first package by drone and the company said that it expected to expand trials in the near future.