Amazon's plans to launch a drone delivery service in the United States are slowly inching forward.

The Federal Aviation Administration just announced an important milestone in drone flight that has significant implications for Amazon and other companies hoping to launch commercial drone operations.

The University of Alaska completed the first FAA-approved "beyond line of sight" drone flight this week, Reuters reported.

Up until now, the agency has had a strictly-enforced "line of sight" rules that requires drone operators to be able to see their drone at all times. And even one-time waivers granted by the FAA have required a person on the ground to watch the drone, according to Iris Automation, a company that makes the collision avoidance software that was used in the Alaska flight. This has been a major hurdle for Amazon and other companies that want to use autonomous drones for delivery services and other uses.

The flight, which was completed in Alaska over an oil pipeline, was a test, but it's still an important milestone for the drone industry. "This is the first time detect and avoid technology is approved by an aviation authority as reliable enough to allow for BVLOS [beyond visual line of sight] drone operations," Alexander Harmsen, CEO of Iris Automation, said in a statement.

Amazon is likely watching these developments closely. The company's still nascent Prime Air service uses drones to deliver packages in some places in Europe, but it hasn't been approved in the United States. In June, the company showed off a new drone design and promised that drone deliveries, which can be completed in as little as 30 minutes, would launch within "months."

In the U.S., there are still a lot of hurdles for Amazon and others to clear before the FAA approves beyond-line-of-sight flights more widely. But a successful first test flight is certainly an encouraging sign for anyone excited about the prospect of even faster Amazon deliveries.