LONDON, Aug. 1 (Xinhua) -- E-commerce giant Amazon has struck a deal with the British government to conduct drone package delivery testing in the country, almost two years after it was banned from such testing by U.S. authorities.

The latest deal allowed Amazon to develop and test technologies in three main areas: when drones can't be seen by their pilots; stopping the drones crashing into buildings; and where one person flies multiple drones at once, The Wired reports, according to a report by Reuters.

In 2013, Amazon revealed its Prime Air program in an interview on 60 Minutes, a plan for Amazon to use drone technology to autonomously deliver individual packages to customers' doorsteps within 30 minutes of ordering.

Google has been working on a plan called Project Wing, hoping to rapidly deliver products across a city by drones with full-scale testing being carried out in Australia.

In a YouTube video that Google has uploaded, it showed off a five-foot single-wing drone that could fly thousands of feet in the air and gently lower packages to the ground using a winch. The tech giant hopes to release its drone delivery service to the public in 2017.

Despite those technical breakthroughs, experts have warned against its possibility.

"It is technically possible to deliver a package by drones but the practice still faces challenges as far as law and safety problems are concerned," said Chen Bingwen, a researcher with Unmanned Aerial Vehicle Research Institute in Beijing, China.

U.S. Federal Aviation Administration (FAA) got in Amazon's way to carry out the plan by refusing to approve Amazon's application to test drones in a rural area outside Seattle in 2014, which has led to the company's relocation of its research and development to Canada, Britain and the Netherlands.

FAA requirements effectively ban drone deliveries by requiring operators to retain a line of sight, avoid flying drones over people, and stick to a low weight limit, according to a report by Wall Street Journal.

Chinese tech companies have not fallen behind their U.S. counterparts and have revealed their own drone delivery plans.

Shunfeng Express, one of the leading express companies in China, has been testing its drone delivery system by flying more than 500 flights per day, hoping to carry packages to the inaccessible countryside and accumulate data for future reference.

JD.com, one of the largest B2C online retailers in China, successfully completed its first drone delivery on June 8, during which a drone carried a package to its destination 10 km away in just 10 minutes.

The company has displayed three types of drones, all of which can carry a package with weight ranging from 10 kg to 15 kg and fly a distance ranging from 5 km to 10 km. After automatically loading its package, the drones can autopilot itself to its base.

The company was reportedly authorized by the air force and the aviation administration to fly under 120m in Suqian, a city in east China's Jiangsu Province.

"Delivery in the sparsely populated countryside can be very costly as it takes too much time and energy just for one package. Drone delivery has perfectly solved this problem," Liu Qiangdong, CEO of JD.com, told Sina Tech.

"If we can use drones on a large scale in the future, the cost of delivery in the countryside can be significantly reduced," said Liu.

But large-scale drone delivery has yet to be possible in China as the Civil Aviation Administration of China (CAAC) requires license or administration by an association, which are not in place, for any unmanned aerial vehicle with wight above 7 kg or flying out of the pilot's sight.

"The flying routes of drones need careful planning to avoid densely populated areas and overcrowding in the airspace, which is not possible under current regulations," said Chen.

"Even if it is granted by the authorities, we still must be very careful about drone delivery simply because of safety issues, for it can easily be used for smuggling, drug trafficking and terrorist purposes," he added.