Amazon.com has won approval from U.S. federal regulators to test a delivery drone outdoors, less than a month after the e-commercgiant blasted regulators for being slow to approve commercial drone testing. The Federal Aviation Administration had earlier given the green light to an Amazon prototype drone in March, but the company told U.S. lawmakers less than a week later that the prototype had already become obsolete while it waited more than six months for the agency's permission.

The FAA granted Amazon's request to test delivery drones in a letter dated Wednesday.

According to the rules set by the FAA, Amazon must keep flights at an altitude of no more than 400 feet and no faster than 100 miles per hour.

Amazon.com wants to use drones to deliver packages to its customers over distances of 10 miles or more, which would require drones to travel autonomously while equipped with technology to avoid collisions with other aircraft.