The ATC system—the second major part of the National Airspace System—offers three basic forms of service: navigation aid (including landing), flight planning and in-flight advisory information, and air traffic control.

Air Traffic Control (ATC) services are divided into three primary categories based on the phase of flight: Tower Control, Terminal (Approach/Departure) Control, and En Route Control. Tower Controllers manage the "active" runways and the immediate airspace around the airport (usually within a 5-mile radius), ensuring safe takeoffs and landings. Terminal Area Controllers (often located in a TRACON facility) manage the transition between the airport and the high-altitude sky, guiding planes as they climb out or descend into a busy metropolitan area (typically up to 30–50 miles away). Finally, En Route Controllers (Center) manage aircraft at high altitudes across vast geographical sectors, ensuring they stay separated as they cruise between cities or across oceans. Together, these three services provide a seamless "hand-off" for every commercial flight from gate to gate.