Retail giant Amazon has filed patents for airborne warehouses from which drones could make deliveries to major cities within minutes, reports have revealed. The patent was originally filed in 2014 and awarded in April 2016 – but only recent circulated.

According to CNBC, these giant airships would float at around 45,000ft with drones flying down to deliver packages. Amazon contends that this would be more energy-efficient, as the drone would glide down.

The patent says that the flying warehouse could also be moved so it is stationed near places of high demand such as major cities, reported the Press Association. Another suggested place was a sporting event where customers could quickly buy merchandise.

Rather than returning to land each time it needed to refuel, the airship would stay airborne, with a smaller shuttle vessel bringing fuel and restocking products.

Amazon started trialling drone deliveries in the UK in early December. Currently the option is available to two customers in rural Cambridgeshire – but there are hopes it can be expanded.

A video released by Amazon showed the drones, stationed at a fulfilment centre near the customers' homes, being packed by staff, before sent out on a runway to a launch pad. When the drone gets near to the customer's house, it scans the ground with a camera to find an Amazon logo that customers place on the ground.

IBTimes UK reached out to Amazon for comment on the patent but did not receive an immediate response.

Amazon's warehouses have been the subject of controversy in the past, with allegations that workers were threatened with termination if they took sick days and that staff at the Dumfermline warehouse were sleeping in tents outside the building to save on costs.