Amazon.com Inc. formally requested permission from the Federal Aviation Administration to start testing drones, an important step toward the online retail giant’s goal to use the devices to deliver packages.

Amazon AMZN, -1.78% first unveiled the plans in December, dubbing the proposed service Amazon Prime Air and saying drones would eventually be able to deliver small packages to customers in less than 30 minutes. In its petition to the FAA, posted Thursday, Amazon said it is now on its eighth- and ninth-generation drone prototypes, including some that can travel more than 50 miles an hour and carry 5-pound packages, which would cover 86% of products it sells.