Final answer:
The license required for professional drone operation in the U.S. is the Part 107 certificate, obtained by passing the FAA's Aeronautical Knowledge Test.
Step-by-step explanation:
The license needed to fly a drone professionally in the United States is called Part 107, which is a part of the Federal Aviation Administration (FAA) regulations. To obtain this certificate, an individual must pass the FAA's Aeronautical Knowledge Test, which covers various topics including airspace classification, weather, drone regulations, and emergency procedures. Once the test is passed, the FAA grants a Remote Pilot Certificate, which is required for those looking to operate drones for commercial purposes.