But there was a hitch, with the company since revealing the vehicle cleared for use had already become obsolete. Things are now back on track with the FAA giving Amazon the green light to put its current models to the test.

Amazon first took steps to win the blessing of the authorities in July last year, when it petitioned the FAA for permission to begin testing its drones. But the agency's response was hardly swift, finally granting an "experimental airworthiness certificate" to Amazon in March 2015. The slow progress partnered with the now-evident worthlessness of the permit prompted Amazon to carry out testing of its more sophisticated models abroad, namely at a secret Canadian site only 2,000 ft (610 m) from the US border.

By way of a letter to Paul Misener, Amazon's vice president of Global Public Policy, on Wednesday April 8, the FAA has granted the company's request for exemption. This will clear the way for Amazon to begin testing its drones outdoors in the United States.