Amazon has revealed further details about how its super fast Prime Air drone delivery program will work, but not how much it will cost customers to use. The much-hyped service will see custom-made weather and environment-adapted unmanned aerial vehicles carrying packages weighing up to 5 pounds within a 10-mile radius of the depot. The devices, fitted with sensors to avoid collisions, will deliver within 30 minutes of customers placing their orders. Paul Misener, the e-commerce giant's vice president for global public policy, told Yahoo! Tech the cost to customers had yet to be determined. But the 5 pound weight limit was decided on after Amazon found that most items it sold weighed less than that.