The National Airspace System Explained

Airport control room
Lester Lefkowitz/The Image Bank/Getty Images

The national airspace system (NAS) was created at the dawn of commercial aviation to get aircraft from point A to point B in a safe and efficient manner. It’s an old system, but it’s worked for us since World War II. In fact, the United States has the safest skies in the world with respect to air transportation.

There are around 7,000 aircraft in the sky above America at once, according to the Federal Aviation Administration (FAA). This number is expected to only increase over the next 15 years, and it continues to get more difficult to fit all these aircraft into our current airspace structure. The FAA’s Next Generation Air Transportation System (NextGen) promises to transform the current airspace system to optimize the use of airspace, reduce emissions, save fuel and decrease flight delays. Until NextGen is fully implemented, though, our current airspace system will have to suffice.


The FAA classifies airspace in one of four categories:

  • Controlled airspace: the airspace around busy airports, along with aircraft routes, and above 18,000 feet. The FAA further divides this airspace in classes A, B, C, D and E airspace, each having different dimensions and rules.
  • Uncontrolled airspace: any airspace that isn’t controlled.
  • Special-use airspace: restricted, prohibited, warning and alert areas, as well as military operations areas (MOAs).
  • Other airspace: airspace used for temporary flight restrictions.

Air Traffic Control Centers

The NAS involves more than just the control tower at your local airport. On a typical flight, a pilot will communicate with controllers at each of the following places:

  • ARTCC - The airspace over the United States is divided into 22 regional sectors, each controlled by an Air Route Traffic Control Center, or ARTCC. As a flight crosses the boundary from one ARTCC region to another, the air traffic controller transfers the communication responsibility for that flight to the ARTCC controller in the next region.
  • TRACON- Terminal Radar Approach Control (TRACON) is known simply as “approach” to pilots. When an aircraft gets close to an airport, the ARTCC controllers will transfer the communications to a TRACON controller, who will assist the aircraft for the arrival portion of its flight.
  • ATCT- Controllers in the local air traffic control tower (ATCT) are responsible for aircraft in the associated airport's traffic pattern. Once the aircraft enters the local airport traffic pattern area, it is handed off to the ATCT, where the controllers will oversee its final approach and landing. Ground controllers are also a part of the ATCT, supervising taxi and gate operations.
  • FSS- There are currently six flight service stations (FSS) in operation. Flight service specialists assist pilots with preflight planning, weather briefings, and other information pertinent to a pilot’s route of flight.


In addition to the many different technologies that have been in use for years, the aviation industry is continuously developing new technologies to make the system more efficient, easier and safer for pilots and controllers. Here are just a few of them:

  • Radar- Currently, the NAS relies heavily on ground-based radar systems to run smoothly. The ground radar emits radio waves, which reflect off aircraft. The signal from the aircraft is then interpreted and sent digitally to computer screens at the ARTCC, TRACON or ATCT.
  • Standard radios- Pilots and controllers communicate directly with VHF (very high frequency) and UHF (ultra-high frequency) radios.
  • CPDLC- Controller Pilot Data Link Communications, as the name implies, is a method for controllers and pilots to communicate via a data link. This type of communication is convenient where radios are not available and also decreases radio congestion.
  • GPS- A type of navigational aid, the Global Positioning System is aviation’s most accurate and most popular means of air navigation and the bread and butter of the NextGen program.
  • ADS-B- In recent years, a system called ADS-B (Automatic Dependent Surveillance-Broadcast) has become popular as a means to assist pilots and controllers in gaining a more accurate picture of air traffic, weather, and terrain during a flight.

The Next Generation Air Transportation System

Our current air traffic system gets airplanes where they need to go in a safe and organized manner, utilizing technology both old and new. While our current national airspace system has worked well for many years, it is hardly optimal for the volume of air traffic in our skies today. We are seeing more crowded runways, airport delays, wasted fuel and lost revenues than ever before. There’s hope, though; the NextGen program is meant to improve upon the current NAS by finding methods to deal with the increased traffic and improve the overall system.