The tech firm based in the city of South San Francisco said its product provides quiet, fast delivery to homes in cities as well as suburbs.

"It's an opportunity for us to really precisely make deliveries, even in high winds," Zipline head of engineering Joseph Mardall told AFP.

Zipline spent several years refining its new platform, in which an electric-powered drone flies along more than 300 feet above the ground to its destination, then releases a "delivery droid" to take packages the final distance.

The droid maneuvers down a tether, dropping off packages in locations as small as a patio table or a front stoop, the company said.

The system is designed to be nearly silent, sounding like wind rustling leaves, and can deliver a package 10 miles away in about 10 minutes, according to its creators.

Several businesses including US salad-centric restaurant chain Sweetgreen have signed on to use Zipline's new delivery system, according to the company.

Zipline said the Government of Rwanda will use the service for "last mile" deliveries to homes, hotels and health facilities in Kigali and elsewhere in the country.

Each new generation "Zip" drone carries a payload weighing from 6 pounds to 8 pounds, according to the company.

Zipline plans to conduct thousands of flight tests this year, then deploy the system to its first customer shortly after that.