Jeff Bezos, the founder and CEO of, recently announced that his company is working on a fleet of autonomous drone aircraft that would deliver packages to your door. When pressed by interviewer Charlie Rose, Bezos said that he hoped the service would be available within “four or five years,” or not long after the U.S. Federal Aviation Administration (FAA) establishes the rules of the skies for commercial drone aircraft in 2015.

Such a rollout is entirely plausible from a technological point of view. Drone aircraft are perfectly tailored to take make short-hop flights from, say, an Amazon distribution warehouse to a nearby suburban home, thereby solving the expensive “last mile” problem of Internet delivery. It’s much easier to program autonomous navigation into a small aircraft than it is to design a self-driving vehicle, as Google is trying to do—the car, after all, has to obey the rules of the road and contend with other drivers, whereas the drone can fly as the crow. And it’s far easier to build a fleet of small, autonomous drones than it is to engineer a space program from scratch, as Bezos has been attempting with his company Blue Origin.

But about those rules. Drone aircraft are complicated pieces of machinery, and the skies are somewhere where U.S. regulatory authorities abide by a philosophy that could best be described as “better safe than sorry.” Drones must not fly into each other, or other aircraft, or the sides of office buildings. They must also be secure against hackers who might try to override their controls and put them to nefarious ends. The University of Texas at Austin engineers Todd Humphreys and Kyle Wesson describe just a few of the challenges facing the FAA in their November story “Hacking Drones,” illustrating the potential danger of out of control drone aircraft with the real-world tale of a U.S. Navy MQ-8B Fire Scout helicopter that stopped responding to commands and flew into the restricted airspace above Washington, D.C., in 2010. The cause? An unspecified “software issue."

Amazon and ambitious companies like it will have to convince the FAA that its drone fleets will not pose unacceptable risks. But in the near term, that conversation is likely to be short. Amazon, after all, is building a fleet of autonomous delivery drones. The FAA’s preliminary list of “general requirements and assumptions” for drone use explicitly state that “autonomous use is not permitted” (PDF link).

Still, Bezos is known to focus on the long-term, and perhaps in a decade or more the FAA may concede that the risks posed by a fleet of autonomous delivery robots may not exceed our appetite for 30-minute delivery. As with any advanced technological system, one must balance potential risk against the reward. “An airplane can still be hijacked, pilots coerced, commu­nications links interrupted,” write Humphreys and Wesson. “Yet we continue to fly, not because we are unaware of the risks but because convenience trumps them. Drones will seek from us the same concession.”