Amazon has received a patent for a shipping label that includes a built-in parachute, “to enable the delivery of packages by [unpiloted] aerial vehicles (UAVs) or other aerial vehicles.” The patent, as reported by GeekWire, was filed in August 2015 and granted by the US Patent and Trademark Office (USPTO) on Monday.

It is unclear whether the system will ever be put into use, though the patent may provide new insight into Amazon’s Prime Air drone delivery project. The system calls for a packaging label that would be integrated with a folded parachute and a network of cords. It could also incorporate a breakaway cover, shock absorbers, and a network of sensors built into a drone to track the package’s descent. The system could be adapted to accommodate an item’s size, and could incorporate several parachutes for heavy packages.

Amazon began trialling its drone delivery system in the UK late last year, and the company completed its first Prime Air demonstration in the US in March. Parachutes didn’t figure into either trial — the autonomous drones simply landed and released their packages — but a patent granted to Amazon in February calls for packages to be released with parachutes mid-flight. Zipline, a California-based startup, has also been using parachutes to deliver blood from drones to remote areas of Rwanda.

Amazon hopes its Prime Air network will eventually deliver packages within 30 minutes, and it has gradually accumulated patents on drone technology and infrastructure. But the company still faces regulatory hurdles in the US, where autonomous drones are still not authorized to fly under current FAA rules.