What is the most busy faa facility?

There are three types of FAA air traffic control facilities that each perform different functions: Tower, Approach Control, and En Route Center. Towers generally control traffic on the airport surface and within a 5 mile radius, Approach Controls use RADAR to separate traffic within a larger, regional airspace around the airport (50 mile radius or more, and surface to about 15000 feet), En Route Centers have airspace spanning thousands of square miles and several states (20 Centers cover the United States.)

By type, the busiest FAA facilities (calendar year 2007 data) are:

Tower: Atlanta Hartsfield TowerApproach Control: Southern California TRACON (covers all LA and San Diego area)Center: Atlanta Center