Drones won't be used for Amazon deliveries yet, it would seem, after draft regulations drawn up by the US's Department of Transportation's Federal Aviation Administration (FAA) asserted that operators of small unmanned aircraft systems (UAS) must maintain visual line of sight.

The framework of regulations would, however, allow routine use of certain small UAS in today's aviation system, while maintaining flexibility to accommodate future technological innovations.

It is this second point that may give Amazon – and other retailers – hope that they could in the future be able to deliver their customers' online orders via this emerging technology.

Indeed, FAA administrator Michael Huerta commented: "We have tried to be flexible in writing these rules.

"We want to maintain today's outstanding level of aviation safety without placing an undue regulatory burden on an emerging industry."

At the end of 2013, Amazon CEO Jeff Bezos hinted that his company was trialling an 'Amazon Prime Air' service, which would see drones deliver parcels to customers' homes, which could reduce the delivery time window to just 30 minutes.

Some in the industry described the comments as a publicity stunt, but the online retailer's research and development team have continued testing new systems, and last year there were reports of the service being tested in India.

The public will be able to comment on the proposed FAA regulations for a 60-day period. Public meetings are also expected to be held to discuss innovation and opportunities at the test sites and forthcoming UAS Centre of Excellence.