Delivery firm UPS has become the first company to be granted permission to fly an unlimited number of delivery drones, at night and out of sight of pilots if it so wishes, in the United States.

The company was granted Part 135 Standard certification by the Federal Aviation Authority at the start of October, meaning it can now push ahead with Flight Forward, a new division focused on creating a commercial drone delivery service.

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Initially, Flight Forward will work with the healthcare industry, using drones to carry critical packages around hospital campuses across the US. Beyond this, the company plans to "transport a variety of items for customers in many industries, and regularly fly drones beyond the operators' visual line of sight."

Part 135 Standard Certification allows UPS to fly drones with cargo of more than 55 pounds, and at night - both of which weren't possible under previous FAA restrictions. The certification also has no limits on the size or scope of operations. Unlike any other company in the US so far, UPS is permitted to fly an unlimited number of drones with an unlimited number of remote pilots.

This certification gives UPS a lead over other prominent companies working on drone delivery services, including Amazon and Uber. Alphabet, parent of Google, also has Part 135 Certification, but only for a single drone pilot employed by the company.

"This is history in the making, and we aren't done yet," said UPS chief executive officer David Abney. "Our technology is opening doors for UPS and solving problems in unique ways for our customers. We will soon announce other steps to build out our infrastructure, expand services for healthcare customers and put drones to new uses in the future."

UPS says its delivery drones will make "regular and frequent" flights which see the aircraft fly beyond the visual line of sight of the operator. The company also said it plans to partner with additional drone manufacturers to "build new drones with varying cargo capacities."

Beyond working around hospitals, UPS wants its drones to serve other industries too, including "the transport of special commodities and other regulated goods."