Introduction

The National Airspace System (NAS) is the network of
United States airspace: air navigation facilities, equipment
services, airports or landing areas, aeronautical charts,
information/services, rules, regulations, procedures, technical
information, manpower, and material. Included are system
components shared jointly with the military. The system's
present configuration is a reflection of the technological
advances concerning the speed and altitude capability of jet
aircraft, as well as the complexity of microchip and satellite-
based navigation equipment. To conform to international
aviation standards, the United States adopted the primary
elements of the classification system developed by the
International Civil Aviation Organization (ICAO).

This chapter is general discussion of airspace classification;
en route, terminal, and approach procedures; and operations
with in the NAS. Detailed information on the classification
of airspace, operation procedures, and restrictions is found
in the Aeronautical Information Manual (AIM).