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AIM

10/12/17

3−1−1

General

Chapter 3. Airspace

Section 1. General

3−1−1. General

a. There are two categories of airspace or airspace

areas:

1. Regulatory (Class A, B, C, D and E airspace

areas, restricted and prohibited areas); and

2. Nonregulatory (military operations areas

[MOA], warning areas, alert areas, controlled firing

areas [CFA], and national security areas [NSA]).

NOTE−

Additional information on special use airspace (prohibited

areas, restricted areas [permanent or temporary], warning

areas, MOAs [permanent or temporary], alert areas,

CFAs, and NSAs) may be found in Chapter 3, Airspace,

Section 4,  Special  Use  Airspace,  paragraphs 3−4−1

through 3−4−8 .

b. Within these two categories, there are four

types:

1. Controlled,

2. Uncontrolled,

3. Special use, and

4. Other airspace.

c. The categories and types of airspace are dictated

by:

1. The complexity or density of aircraft

movements,

2. The nature of the operations conducted

within the airspace,

3. The level of safety required, and

4. The national and public interest.

d. It is important that pilots be familiar with the

operational requirements for each of the various types

or classes of airspace. Subsequent sections will cover

each class in sufficient detail to facilitate

understanding.

3−1−2. General Dimensions of Airspace

Segments
Refer to Code of Federal Regulations (CFR) for

specific dimensions, exceptions, geographical areas

covered, exclusions, specific transponder or equip-

ment requirements, and flight operations.

3−1−3. Hierarchy of Overlapping Airspace

Designations

a. When overlapping airspace designations apply

to the same airspace, the operating rules associated

with the more restrictive airspace designation apply.

b. For the purpose of clarification:

1. Class A airspace is more restrictive than

Class B, Class C, Class D, Class E, or Class G

airspace;

2. Class B airspace is more restrictive than

Class C, Class D, Class E, or Class G airspace;

3. Class C airspace is more restrictive than

Class D, Class E, or Class G airspace;

4. Class D airspace is more restrictive than

Class E or Class G airspace; and

5. Class E is more restrictive than Class G

airspace.

3−1−4. Basic VFR Weather Minimums

a. No person may operate an aircraft under basic

VFR when the flight visibility is less, or at a distance

from clouds that is less, than that prescribed for the

corresponding altitude and class of airspace. 

(See TBL 3−1−1.)

NOTE−

Student pilots must comply with 14 CFR Section 61.89(a)

(6) and (7).

b. Except as provided in 14 CFR Section 91.157,

Special VFR Weather Minimums, no person may

operate an aircraft beneath the ceiling under VFR

within the lateral boundaries of controlled airspace

designated to the surface for an airport when the

ceiling is less than 1,000 feet.  (See 14 CFR

Section 91.155(c).)

3/29/18

AIM