National Airspace System

Depending on the class of airspace and flight conditions, communication with air traffic controllers may or may not be required.

Operation of each flight is always the responsibility of the pilot in command, but air traffic controllers give instructions for sequencing and safety as needed.

Approximately 14,500 air traffic controllers, 4,500 aviation safety inspectors, and 5,800 technicians operate and maintain services for the NAS.

In addition, there are over 71,000 pieces of equipment, ranging from radar systems to communication relay stations.

It is the most controlled airspace and requires a pilot to carry an Instrument Flight Rating and proper clearance no matter what type of aircraft is being flown.

[6] Class B airspace extends from the surface up to 10,000 ft. AGL and is the area above and around the busiest airports (e.g., LAX, MIA, CVG) and is also heavily controlled.

A side view of Class B airspace resembles an upside-down wedding cake with three layers becoming bigger toward the top.

Pilots are required to establish and maintain two-way radio communications with the ATC facility providing air traffic control services prior to entering the airspace.

Pilots using Visual Flight Reference must be vigilant for traffic as there is no positive separation service in the airspace.

Pilots in these areas are responsible for position and separation and may use a specified Common Traffic Advisory Frequency (CTAF) or UNICOM for that airport, although no-radio flight is also permitted.