A century after the Wright Brothers' first flight, it's not the physics that are stopping a second aviation revolution, it's the laws. Amazon wants to start using its fleet of drones for delivery as soon as possible, but first it needs the US government to greenlight them. As Amazon vice president of global policy Paul Misener said said today during a hearing before Congress: "we'd like to begin delivering to our customers as soon as it's approved." For that to happen, Amazon needs the FAA to change how it regulates unmanned aircraft, and that idea might be tough to get off the ground in the near term.

Amazon's objective, like that of many companies seeking to use drones, is to combine the speed and efficiency of flight with somewhat automated programming, so that drones can travel to programmed-in locations and deliver goods. Amazon first announced their plan late in 2013, and it was greeted with some skepticism.

Despite that, Amazon appears to be earnestly pursuing the drone delivery dream. In this process, they've butted heads with the FAA on a number of occasions, arguing that the rules are too restrictive in the United States to allow them to develop here, and then getting permission to test drones, but not at all in the way that Amazon wants.