Introduction to Airspace

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Airspace can be defined as the imaginary boundaries of the atmosphere where aircraft flight operations are conducted. There are two categories of airspace: Regulatory and Nonregulatory. Regulatory airspace includes Class A, B, C, D, E airspace, restricted areas, and prohibited areas. Nonregulatory areas consists of military operations areas (<abbr title="Military Operations Area">MOA</abbr>), warning areas, alert areas, and controlled firing areas (<abbr title="Controlled Firing Area">CFA</abbr>), and national security areas (<abbr title="National Security Area">NSA</abbr>). There is no Class F airspace in the U.S. National Aerospace System.

Within these two categories, there are four types:
1. Controlled
2. Uncontrolled
3. Special use
4. Other airspace

The categories and types of airspace are dictated by the complexity or density of aircraft movements, the nature of the operations conducted, the level of safety required, and both national and public interest. Pilots must be familiar with the operating requirements within all airspace to maintain the safety of flight.

Controlled airspace is the term used to refer to the different classifications of airspace (Class A, B, C, D, and E) and defined dimensions within which air traffic control service is provided to <abbr title="Instrument Flight Rules">IFR</abbr> flights and to <abbr title="Visual Flight Rules">VFR</abbr> flights in accordance with the airspace classification. Services provided to aircraft include <abbr title="Instrument Flight Rules">IFR</abbr> separation, traffic advisories, and safety alerts (both terrain/obstruction and aircraft conflict/mode intruder alerts).

What is Airspace?

**Basic <abbr title="Visual Flight Rules">VFR</abbr> Weather Minimums**

Pilots operating under Visual Flight Rules (<abbr title="Visual Flight Rules">VFR</abbr>) are required to see and avoid other aircraft and obstacles to remain safe. Therefore, no person may operate an aircraft under <abbr title="Visual Flight Rules">VFR</abbr> when the minimum flight visibility or distance from clouds cannot be maintained within a specific class of airspace.


_Basic <abbr title="Visual Flight Rules">VFR</abbr> Weather Minimums Table_

| **Airspace** | **Flight Visibility** | **Distance from Clouds** |
| -------- | -------- | -------- |
| **Class A** | Not Applicable | Not Applicable |
| **Class B** | 3 statute miles | Clear of Clouds |
| **Class C** | 3 statute miles | 500 feet below 1,000 feet above 2,000 feet horizontal |
| **Class D** | 3 statute miles | 500 feet below 1,000 feet above 2,000 feet horizontal |
| **Class E** - _less than 10,000 feet <abbr title="Mean Sea Level">MSL</abbr>_ | 3 statute miles | 500 feet below 1,000 feet above 2,000 feet horizontal |
| **Class E** - _at or above 10,000 feet <abbr title="Mean Sea Level">MSL</abbr>_ | 5 statute miles | 1,000 feet below 1,000 feet above 1 statute mile horizontal |
| **Class G** - _1,200 feet or less above the surface (regardless of <abbr title="Mean Sea Level">MSL</abbr> altitude)_ Day, except as provided in section §91.155(b) | 1 statute mile | Clear of Clouds |
| **Class G** - _1,200 feet or less above the surface (regardless of <abbr title="Mean Sea Level">MSL</abbr> altitude)_ Night, except as provided in section §91.155(b) | 3 statute miles | 500 feet below 1,000 feet above 2,000 feet horizontal |
| **Class G** - _More than 1,200 feet above the surface but less than 10,000 feet <abbr title="Mean Sea Level">MSL</abbr>)_ Day | 1 statute mile | 500 feet below 1,000 feet above 2,000 feet horizontal |
| **Class G** - _More than 1,200 feet above the surface but less than 10,000 feet <abbr title="Mean Sea Level">MSL</abbr>)_ Night | 3 statute miles | 500 feet below 1,000 feet above 2,000 feet horizontal |
| **Class G** - _More than 1,200 feet above the surface and at or above 10,000 feet <abbr title="Mean Sea Level">MSL</abbr>)_ | 5 statute miles | 1,000 feet below 1,000 feet above 1 statute mile |



**Basic <abbr title="Visual Flight Rules">VFR</abbr> Cruising Altitudes**

In addition to weather minimums, pilots are also required to fly at different cruising altitudes based on the direction of their aircraft's flight path (ground track); these cruising altitudes only apply when an aircraft is flying more than 3,000 feet about the surface.


_Basic <abbr title="Visual Flight Rules">VFR</abbr> Cruising Altitudes Table_

| **If your magnetic course (ground track) is:** | **And you are more than 3,000 feet above the surface but below 18,000 feet <abbr title="Mean Sea Level">MSL</abbr>** | **And you are above 18,000 feet <abbr title="Mean Sea Level">MSL</abbr> to <abbr title="Flight Level">FL</abbr>290, fly:** |
| -------- | -------- | -------- |
| 0&deg; to 179&deg; | 	Odd thousands <abbr title="Mean Sea Level">MSL</abbr>, plus 500 feet (i.e.: 3,500; 5,500, etc.) | Odd Flight Levels plus 500 feet (i.e.: <abbr title="Flight Level">FL</abbr>195, <abbr title="Flight Level">FL</abbr>215, etc.) |
|180&deg; to 359&deg; | 	Even thousands <abbr title="Mean Sea Level">MSL</abbr>, plus 500 feet (i.e.: 4,500; 6,500, etc.) | Even Flight Levels plus 500 feet (i.e.: <abbr title="Flight Level">FL</abbr>185, <abbr title="Flight Level">FL</abbr>205, etc.) |

_Note: Altitudes are referred to as Flight Levels (<abbr title="Flight Level">FL</abbr>) when aircraft are flying at or above 18,000 feet <abbr title="Mean Sea Level">MSL</abbr>. (i.e.: 35,000 feet <abbr title="Mean Sea Level">MSL</abbr> would be referred to as <abbr title="Flight Level">FL</abbr>350)_

Basic VFR Weather Minimums and Cruising Altitudes

Class A airspace is controlled airspace that extends from 18,000 feet <abbr title="Mean Sea Level">MSL</abbr> up to and including <abbr title="Flight Level">FL</abbr>600 (60,000 feet <abbr title="Mean Sea Level">MSL</abbr>). Altitudes within Class A airspace is referred to as Flight Levels (<abbr title="Flight Level">FL</abbr>). Class A airspace is not depicted on any aeronautical charts, but covers the entire U.S. and extends horizontally 12 nautical miles off the coast of the 48 contiguous States and Alaska within areas of domestic radio navigational signal or <abbr title="Air Traffic Controller">ATC</abbr> radar coverage, and within which domestic produces are applied. Pilots who operate in this airspace use Instrument Flight Rules (<abbr title="Instrument Flight Rules">IFR</abbr>) that show established air routes.

In order for <abbr title="Air Traffic Controller">ATC</abbr> to maintain proper separation of aircraft operating in Class Airspace, all aircraft are required to set the aircraft's altimeter to the standard setting of 29.92 Hg; this ensures all pilots are maintaining a given altitude based on the same reference point.

Below are the requirements and other information pertaining to Class A airspace.

| Item | Requirements |
| -------- | -------- |
| Type | Controlled |
| Entry Requirements | <abbr title="Air Traffic Controller">ATC</abbr> Clearance & <abbr title="Instrument Flight Rules">IFR</abbr> Flight Plan |
| Minimum Pilot Qualifications | Instrument Rating |
| Minimum Aircraft Equipment | <abbr title="Instrument Flight Rules">IFR</abbr> Equipped |
| Two-way Radio Communications | Yes |
| Special <abbr title="Visual Flight Rules">VFR</abbr> | No |
| <abbr title="Visual Flight Rules">VFR</abbr> Traffic Sequencing & Separation | Not applicable |
| Traffic Advisories | Yes |
| Airport Application | None |
| Speed Restrictions | None |

Class A Airspace

Class B airspace is controlled airspace that is established to separate the flow of all airport arrivals and departures; this is why Class B airspace is usually found at major airports around the world. Class B airspace is depicted on Sectional Charts, <abbr title="Instrument Flight Rules">IFR</abbr> En Route Low Altitude Charts, and Terminal Area Charts as a solid blue line. It usually has a series of solid blue lines surrounding each other and its shape is tailored to the airport's departure and arrival routes. Terrain and other land features also influence the boundaries of Class B airspace.

Some Class B airspace surrounding airports resemble an upside down wedding cake with multiple layers; this is because the airspace usually starts at the surface extending a smaller radius than the layers starting at higher altitudes. The floor and ceilings of Class B airspace is denoted on aeronautical charts by <abbr title="Mean Sea Level">MSL</abbr> altitudes.

The airspace within 30 miles of an airport, generally surrounding primary airports within Class B airspace areas from the surface up to 10,000 feet <abbr title="Mean Sea Level">MSL</abbr>, is considered a Mode C Veil. When a Mode C Veil is present, aircraft operating within this airspace must be equipped with automatic pressure altitude reporting equipment having mode C capability. "Having mode C capability" means that the aircraft's current altitude is reported by it's transponder.

Aircraft entering and departing Class B airspace require an <abbr title="Air Traffic Controller">ATC</abbr> clearance. When departing Class B airspace, <abbr title="Visual Flight Rules">VFR</abbr> traffic should advise the controller of their intended altitude and route of flight. <abbr title="Air Traffic Controller">ATC</abbr> will normally advise <abbr title="Visual Flight Rules">VFR</abbr> aircraft when leaving the geographical limits of Class B airspace. Radar service is not automatically terminated with this advisory unless specifically stated by the controller.

If an aircraft wishes to transition through Class B airspace, it must obtain an <abbr title="Air Traffic Controller">ATC</abbr> clearance to do so. A clearance is provided as traffic conditions and workload permit. For this reason, aircraft are encouraged to fly at altitudes above or below Class B airspace or use established <abbr title="Visual Flight Rules">VFR</abbr> corridors.


Below are the requirements and other information pertaining to Class B airspace.

| Item | Requirements |
| -------- | -------- |
| Type | Controlled |
| Entry Requirements | <abbr title="Air Traffic Controller">ATC</abbr> Clearance |
| Minimum Pilot Qualifications | Private Certificate. However a student or recreational pilot may operate within this airspace with appropriate endorsement if requirements of §61.95 are met. Other local restrictions may apply. |
| Minimum Aircraft Equipment | Two-way Radio, Transponder with automatic altitude reporting capability |
| Two-way Radio Communications |	Yes |
| Special <abbr title="Visual Flight Rules">VFR</abbr> |	Yes |
| <abbr title="Visual Flight Rules">VFR</abbr> Traffic Sequencing & Separation |	Yes |
| Traffic Advisories |	Yes |
| Airport Application |	Radar, Instrument, Approaches, Weather, Control Tower, High Density |
| Speed Restrictions | 250 <abbr title="Knots Indicated Airspeed">KIAS</abbr> below 10,000 feet <abbr title="Mean Sea Level">MSL</abbr> within airspace 200 <abbr title="Knots Indicated Airspeed">KIAS</abbr> in areas underlying Class B airspace |

Class B Airspace

Class C airspace is controlled airspace that generally extends from the surface to 4,000 feet <abbr title="Mean Sea Level">MSL</abbr> above the airport elevation and surrounding airports that have an operational control tower, are serviced by a radar approach control, and that have a certain number of <abbr title="Instrument Flight Rules">IFR</abbr> or passenger operations. Class C is tailored to the surrounding area and usually consists of a 5 nautical mile core radius (surface up to 4,000 feet <abbr title="Mean Sea Level">MSL</abbr>) and a 10 nautical mile shelf (1,200 feet up to 4,000 feet above the airport elevation). This airspace is charted on Sectional Charts, <abbr title="Instrument Flight Rules">IFR</abbr> En Route Low Altitude, and Terminal Area Charts, where appropriate, as a solid magenta circle.

Below are the requirements and other information pertaining to Class C airspace.

| Item | Requirements |
| -------- | -------- |
| Type | Controlled |
| Entry Requirements | Two-way Radio Communications prior to entry |
| Minimum Pilot Qualifications | No specific requirement |
| Minimum Aircraft Equipment | Two-way Radio Capable, Transponder with automatic altitude reporting capability |
| Two-way Radio Communications | Yes |
| Special <abbr title="Visual Flight Rules">VFR</abbr> |	Yes |
| <abbr title="Visual Flight Rules">VFR</abbr> Traffic Sequencing & Separation | Yes, workload permitting |
| Traffic Advisories | Yes |
| Airport Application |	Radar, Instrument, Approaches, Weather, Control Tower |
| Speed Restrictions | 250 <abbr title="Knots Indicated Airspeed">KIAS</abbr> below 10,000 feet <abbr title="Mean Sea Level">MSL</abbr>; 200 <abbr title="Knots Indicated Airspeed">KIAS</abbr> below 2,500 feet <abbr title="Above Ground Level">AGL</abbr> within 4 nautical miles of primary airport |

Class C Airspace

Class D airspace is controlled airspace that usually extends from the surface up to 2,500 feet <abbr title="Mean Sea Level">MSL</abbr> above airport elevation surrounding airports that have an operational control tower. This airspace is also tailored specifically to accommodate an airport published instrument procedures. If instrument procedures are published for an airport with Class D airspace, the tower operations will be listed in the Chart Supplement informing the pilot whether the tower is part-time or full-time. Where a Class D surface area is part-time, the airspace may revert to either a Class E surface area or Class G airspace. When a part-time Class D surface area changes to Class G, the surface area becomes Class G airspace up to, but not including, the overlying controlled airspace. Normally, the overlying controlled airspace is the Class E transition area airspace that being at either 700 feet or 1,200 feet <abbr title="Above Ground Level">AGL</abbr> - this can be determined by consulting the applicable <abbr title="Visual Flight Rules">VFR</abbr> Sectional or Terminal Area Charts.

Below are the requirements and other information pertaining to Class D airspace.

| Item | Requirements |
| -------- | -------- |
| Type | Controlled, may be on part-time basis |
| Entry Requirements |	Two-way Radio Communications |
| Minimum Pilot Qualifications |	No specific requirement |
| Minimum Aircraft Equipment | Two-way Radio |
| Two-way Radio Communications |	Yes |
| Special <abbr title="Visual Flight Rules">VFR</abbr>	| Yes |
| <abbr title="Visual Flight Rules">VFR</abbr> Traffic Sequencing & Separation | None |
| Traffic Advisories |	Workload permitting |
| Airport Application |	Instrument, Approaches, Weather, Control Tower |
| Speed Restrictions | 250 <abbr title="Knots Indicated Airspeed">KIAS</abbr> below 10,000 feet <abbr title="Mean Sea Level">MSL</abbr>; 200 <abbr title="Knots Indicated Airspeed">KIAS</abbr> below 2,500 feet <abbr title="Above Ground Level">AGL</abbr> within 4 nautical miles of primary airport |

Class D Airspace

Class E airspace is a type of controlled airspace that is designated to serve a variety of terminal or en route purposes such as an area designated for an airport where a control tower is not in operation, an extension to a surface area, en route domestic areas, airspace used for transition, Federal Airways and Low-Altitude <abbr title="Area Navigation">RNAV</abbr> routes, and offshore areas. Class E dimensions consist of three depictions.

1. The dashed magenta line indicated Class E begins at the surface and extends up to the overlying controlled airspace
2. The magenta vignette on sectional charts, showing that Class E areas extend upward from either 700 feet <abbr title="Above Ground Level">AGL</abbr> or the blue vignette, showing that Class E starts at 1,200 feet <abbr title="Above Ground Level">AGL</abbr> and are designated for airports with an approved instrument procedure.
3. Airways that start at 1,200 feet <abbr title="Above Ground Level">AGL</abbr> to, but not including, 18,000 feet <abbr title="Mean Sea Level">MSL</abbr> and continues above <abbr title="Flight Level">FL</abbr>600.

Class E airspace also extends horizontally 12 miles from the coast of the 48 contiguous states and Alaska.

Below are the requirements and other information pertaining to Class E airspace.

| Item | Requirements |
| -------- | -------- |
| Type | Controlled in some areas |
| Entry Requirements |	<abbr title="Air Traffic Controller">ATC</abbr> Clearance for <abbr title="Instrument Flight Rules">IFR</abbr>. None for <abbr title="Visual Flight Rules">VFR</abbr> |
| Minimum Pilot Qualifications | No specific requirement |
| Minimum Aircraft Equipment | No specific requirement |
| Two-way Radio Communications | Yes, if under <abbr title="Instrument Flight Rules">IFR</abbr> flight plan |
| Special <abbr title="Visual Flight Rules">VFR</abbr> |	Yes |
| <abbr title="Visual Flight Rules">VFR</abbr> Traffic Sequencing & Separation |	None |
| Traffic Advisories | Workload permitting |
| Airport Application	| Instrument, Approaches, Weather |
| Speed Restrictions | Not Applicable |

Class E Airspace

Class G airspace is uncontrolled airspace that has not been designated as either Class A, B, C, D or E airspace. Class G airspace usually extends from the surface to the base of the overlying region, Class E airspace (usually at 700 - 1200 feet <abbr title="Above Ground Level">AGL</abbr>). However, in some high terrain areas Class G can extend as far as 14,500 feet <abbr title="Mean Sea Level">MSL</abbr>. Pilots are reminded that in addition to altitude or flight level requirements to remain at least 1,000 feet (2,000 feet in designated mountainous terrain) above the highest obstacle within a horizontal distance of 4 nautical miles from the course flown. Pilots are required to hold at least a Student Pilot Certificate to operate within this airspace.

In addition to the basic weather minimums, below are the requirements and other information for operating in Class G airspace.

| Item | Requirements |
| -------- | -------- |
| Type | Uncontrolled |
| Entry Requirements |	None |
| Minimum Pilot Qualifications |	No specific requirement |
| Minimum Aircraft Equipment |	No specific requirement |
| Two-way Radio Communications |	Not required |
| Special <abbr title="Visual Flight Rules">VFR</abbr> |	None |
| <abbr title="Visual Flight Rules">VFR</abbr> Traffic Separation |	None |
| Traffic Advisories |	Not applicable |
| Airport Application |	Control Tower |
| Speed Restrictions |	Not Applicable |

Class G Airspace

When one or more airspace overlaps another, the airspace with the more restrictive operating rules should be followed where applicable. For the purpose of clarification:
- Class A airspace is more restrictive than Class B, C, D, E, or G.
- Class B airspace is more restrictive than Class C, D, E, or G.
- Class C airspace is more restrictive than Class D, E, or G.
- Class D airspace is more restrictive than Class E or G.
- Class E airspace is more restrictive than Class G.

Hierarchy of Overlapping Airspace Designations

The <abbr title="Federal Aviation Administration">FAA</abbr> defines special use airspace as any airspace where activity must be confined due to its nature and/or limitations exist for those aircraft not participating in such activities. Special use airspace includes prohibited areas, restricted areas, warning areas, military operations areas, alert areas, control firing areas, and national security areas.


**Prohibited Area**

Prohibited areas are established for security or other reasons associated with the national welfare. These areas are published in the Federal Register and are depicted on aeronautical charts.


**Restricted Area**

Restricted areas are established to prevent aircraft from unusual or often invisible hazards such as artillery firing, aerial gunner, or guided missiles. Pilots must obtain permission from the controlling agency before flying through a restricted area. These areas are also published in the Federal Register.


**Warning Area**

A warning area is airspace of defined dimensions, extending from three nautical miles outward from the coast of the U.S., that contains activity that may be hazardous to nonparticipating aircraft. The purpose of such warning areas is to warn nonparticipating pilots of the potential danger. A warning area may be located over domestic or international waters or both.


**Military Operations Area (<abbr title="Military Operations Area">MOA</abbr>)**

<abbr title="Military Operations Area">MOA</abbr>s are established to separate military training activities such as air combat tactics, aerobatics, formation training, low-altitude tactics, and others from <abbr title="Instrument Flight Rules">IFR</abbr> traffic. <abbr title="Military Operations Area">MOA</abbr>s may also include aircraft flying at speeds greater than 250 knots below 10,000 feet <abbr title="Mean Sea Level">MSL</abbr> within an active <abbr title="Military Operations Area">MOA</abbr>. Although <abbr title="Visual Flight Rules">VFR</abbr> traffic is not prevented from operating within an <abbr title="Military Operations Area">MOA</abbr>, pilots should exercise extreme caution and are encouraged to contact a Flight Service Station within 100 miles of the area to obtain information regarding the <abbr title="Military Operations Area">MOA</abbr>. Prior to entry pilots should contact the controlling agency for traffic advisories.


**Alert Area**

Alert areas are shown on aeronautical charts to inform pilots of areas where a high volume of pilot training or unusual aerial activity such as parachute jumping or student pilot training exists. All pilots are responsible for collision avoidance within and while transitioning through alert areas.


**Controlled Firing Area**

The distinguishing feature of Controlled Firing Areas, as compared to other special use airspace, is that its activities are suspended immediately when spotter aircraft, radar, or ground lookout positions indicate an aircraft might be approaching the area. <abbr title="Controlled Firing Area">CFA</abbr> are not depicted on aeronautical charts since these areas do not cause a nonparticipating aircraft to change its flight path.


**National Security Area**

National Security Areas consist of locations where there is a requirement for increased security and safety of ground facilities. Pilots are encouraged to voluntarily avoid these areas. When necessary, temporary restrictions may be established to prevent aircraft within these areas. If restrictions exist, pilots are informed via Notices to Airmen (<abbr title="Notice to Airmen">NOTAM</abbr>).

Special Use Airspace

**Airport Advisory/Information Services**

Airport Advisory/Information Services is established to provide pilots with information during fast-changing weather and enhance overall safety for pilots operating at busy airports. There are three advisory types: (1) The Local Airport Advisory, which is available only in Alaska and is operated within 10 statute miles of an airport where a control tower is not operating but where an <abbr title="Flight Service Station">FSS</abbr> is located on the airport; (2) Final Guard, which provides pilots with wind/altimeter monitoring service during active weather situations; and (3) the Remote Airport Information Service (<abbr title="Remote Airport Information Service">RAIS</abbr>), which provide information via <abbr title="Notice to Airmen">NOTAM</abbr> D only and is meant to support pilots flying short to medium flights.


**Military Training Routes**

Military Training Routes are established to allow military pilots an area for training. These routes are generally established below 10,000 feet <abbr title="Mean Sea Level">MSL</abbr> for operations in excess of 250 <abbr title="Knots Indicated Airspeed">KIAS</abbr>. There are two types of training routes: <abbr title="Instrument Flight Rules">IFR</abbr> Military Training routes, which are conducted regardless of weather conditions and <abbr title="Visual Flight Rules">VFR</abbr> Military Training routes, which are conducted in accordance with <abbr title="Visual Flight Rules">VFR</abbr> conditions but with 5 miles or greater flight visibility and 3,000 feet <abbr title="Above Ground Level">AGL</abbr> or higher.


**Temporary Flight Restrictions (<abbr title="Temporary Flight Restriction">TFR</abbr>)**

<abbr title="Temporary Flight Restriction">TFR</abbr>s are imposed to protect persons and property in the air or on the surface from an existing or imminent hazard associated with an incident on the surface when the presence of low-flying aircraft would magnify, alter, spread, or compound the hazard. Pilots can find information relating to <abbr title="Temporary Flight Restriction">TFR</abbr>s on the <abbr title="Federal Aviation Administration">FAA</abbr> website and Notices to Airmen (<abbr title="Notice to Airmen">NOTAM</abbr>). Flight Service Stations (<abbr title="Flight Service Station">FSS</abbr>) nearest the <abbr title="Temporary Flight Restriction">TFR</abbr> is usually the coordination facility where pilots may also request information about a <abbr title="Temporary Flight Restriction">TFR</abbr>.


**Parachute Jump Aircraft Operations**

Pilots should always exercise extreme caution when operating an aircraft near airspace where parachute jump operations are being conducted. Pilots engaging in parachute jump operations must follow specific procedures outlined in 14 <abbr title="Code of Federal Regulations">CFR</abbr> Part 105. Prior to conducting a jump operation, the pilot should broadcast the aircraft's altitude and position in relation to the airport, the approximate relative time when the jump will commence and terminate, and listen to the position reports of other aircraft in the area.


**Published <abbr title="Visual Flight Rules">VFR</abbr> Routes**

Published <abbr title="Visual Flight Rules">VFR</abbr> routes help aircraft transition around, under and through complex airspace such as Class B airspace. There are three types of Published <abbr title="Visual Flight Rules">VFR</abbr> routes: (1) <abbr title="Visual Flight Rules">VFR</abbr> Flyways, which can be found on the back side of some sectional charts, provided pilots with recommended routes for operating near complex airspace; (2) <abbr title="Visual Flight Rules">VFR</abbr> Corridors, which are like a hole between Class B airspace that has defined lateral and vertical boundaries; and (3) Class B Airspace <abbr title="Visual Flight Rules">VFR</abbr> Transition Routes, which accommodate <abbr title="Visual Flight Rules">VFR</abbr> traffic through a specific flight course depicted on a Terminal Area Chart (<abbr title="Terminal Area Chart">TAC</abbr>) for transiting a specific Class B airspace. Pilots must obtain <abbr title="Air Traffic Controller">ATC</abbr> clearance for flying Class B Airspace <abbr title="Visual Flight Rules">VFR</abbr> Transition Routes, as these routes require <abbr title="Air Traffic Controller">ATC</abbr>-assigned altitudes.


**Terminal Radar Service Area (<abbr title="Terminal Radar Service Area">TRSA</abbr>)**

Terminal Radar Service Areas are areas where participating aircraft can receive additional radar services. The primary airport(s) within the <abbr title="Terminal Radar Service Area">TRSA</abbr> become(s) Class D airspace. The remaining portion of the <abbr title="Terminal Radar Service Area">TRSA</abbr> overlies other controlled airspace which is normally Class E airspace beginning at 700 or 1,200 feet and established transition to/from the en route/terminal environment. Participation is voluntary, but pilots are encourage to contact the radar approach control and take advantage of <abbr title="Terminal Radar Service Area">TRSA</abbr> service.


**National Security Area (<abbr title="National Security Area">NSA</abbr>)**

National Security Areas consists of airspace of defined vertical and lateral dimensions established at locations where there is a requirement for increased security and safety of ground facilities. Flight in <abbr title="National Security Area">NSA</abbr>s may be temporarily prohibited by regulations, disseminated via <abbr title="Notice to Airmen">NOTAM</abbr>. Pilots are requested to voluntarily avoid flying through these depicted areas.

Other Airspace Areas

FAA Aeronautical Information Publication (AIP) 25th Edition, pg. ENR 1.4-1

FAA-H-8083-25B: Pilot's Handbook of Aeronautical, pg. 15-1

All aeronautical charts include a legend that can be referred to for clarification of chart symbols examples of how airspace is depicted.

When planning a cross-country flight, avoid airspace that can be hazardous to the flight of an aircraft while conducting flight within those areas.

Memorizing the following can help you remember airspace: A - Altitude (18,000 ft to <abbr title="Flight Level">FL</abbr>600), B - Big jets, big airports, C - Crowded (approach control, etc.), D - Dialog (talk to tower), E - Everything Else (anything not A, B, C, or D), G - Go for it! (very few rules, just go for it!)

Most people get Class E and Class G confused, just remember Class G is everywhere you DO NOT see airspace labeled and starts from the Earth's surface extending up to 10,000 ft

Introduction to Airspace

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