The meaning of National Airspace System (NAS) is a chain of airspaces that are above or below your head and essential information about them like navigation, air charts, instruments, airports and rules, and regulations. Read more about the National Airspace System below.
There are six categories of airspaces in NAS that are labeled from letter A to F. These six categories are subdivided into uncontrolled and controlled airspaces. Airspaces that are monitored and controlled by the air-traffic controller (ATC) are under the controlled category of airspaces. The air-traffic does not monitor and control the uncontrolled airspaces.
Class A airspaces lie in the controlled category, and they must be under instrument conditions. Class A airspaces are from 18,000 feet mean sea level (MSL) to 600 flight level (FL), inclusive of the airspace that are overlying the waters that are within 12 nautical miles (NM) of the 48 contiguous states' coasts and Alaska. Class B airspaces are popular because they are in the majority of busy airports like emplacing passengers and other activities.
Class C and D airspaces are reserved for airports that require heavy traffic training and smaller and less busy airports. Airports that have no towers but their spaces are controlled use Class E airspaces. Class G airspaces are controlled by ATC if they are related to the temporary control flow but by the weather of altitude and are generally uncontrolled.
NAS uses the weather because it enables the pilot to choose the right direction to fly to. The weather patterns of the areas the pilot will fly into are studies by the aviation sectionals and Airport Facility Directory (AFD) and notifications are sent to the pilot. The body that defines what should or should not be done in the aviation industry is the Federal Aviation Regulations (FARs). Everything in NAS is defined by Airmen's Information Manual. The pilot operates under the Instrument Flight Rules (IFR).
The vital roles of ATC are to update flights automatically, reduce head downtime, increase safety everyone and everything on the aircraft, quicken and fasten rescheduling of flights, managing aircrafts thus reducing the number of aircraft that are in departure queue and movement area, enhancing the functionality of the Command Centre, TRACON and ARTCC and more.
Aircraft can be held at the movement area or at the gate instead of being held in the long departure line on the taxiway, as usual, improve the predictability of the schedule, increase reliability of connection, and other benefits. Their role also includes reducing the Carbon dioxide footprint in the airport, ensuring resources at the airport are utilized optimally and reduce the noise of the aircraft's' engines.