Federal Aviation Administration
The Federal Aviation Association is the governing body over aviation, which G-Man works for. It administers tests to prospective pilots and grants them pilot's licenses when they succeed.[1]
History
Working under the FAA, G-Man administered a written test and checkride to Gordon Freeman, which he passed, allowing him to obtain a private pilot's license.
The FAA was the ultimate cause of the destruction of the universe, after it tried to administer a test to itself, causing a paradox.[2]