Amazon has been testing its Prime Air delivery drones for years now, but this week IT made its first public demo of the system in the US. A Prime Air drone dropped off some bottles of sunscreen for attendees at the company’s invite-only MARS conference in California on Monday. (MARS stands for machine learning, automation, robotics, and space exploration — it’s also where Amazon CEO Jeff Bezos piloted a giant robot). And although the order was prearranged, the delivery itself was fully autonomous.

Amazon says it’s the first time its drones have flown for the public in America, with all other US flights taking place on private property. It’s not the first public flight ever, though, with the company making a pre-arranged delivery in the UK last December. In a statement given to The Verge, Amazon Prime Air vice president Gur Kimchi said the flight brings the company “one step closer to making 30-minute package delivery by drone a reality,” adding that the delivery was conducted “with the assistance of the FAA.”

This last point is the most interesting, because despite all the work Amazon has put into this concept, it still needs regulatory approval if it’s ever going to operate at scale. Autonomous drone delivery is still prohibited in the US, and Amazon has complained that the regulatory system is too slow to adapt. It’s moving faster in the UK, explaining why Amazon does a lot of testing there, but the biggest problem for tech companies and regulators alike is arranging for reliable low-altitude air traffic control. Something Amazon certainly didn’t have to worry about for this particular test run.

UPDATE: This story has been updated to note that the drone delivery took place in California, not Florida.