AIM 

4/20/23 

1. 

At least 1 statute mile flight visibility for operations within Class B, Class C, Class D, and Class E surface 

areas. 

2. 

At least 1 statute mile ground visibility if taking off or landing. If ground visibility is not reported at that 

airport, the flight visibility must be at least 1 statute mile. 

3. 

The restrictions in subparagraphs 1 and 2 do not apply to helicopters. Helicopters must remain clear of 

clouds and may operate in Class B, Class C, Class D, and Class E surface areas with less than 1 statute mile 

visibility. 

b. 

When a control tower is located within the Class B, Class C, or Class D surface area, requests for clearances 

should be to the tower. In a Class E surface area, a clearance may be obtained from the nearest tower, FSS, or 

center. 

c. 

It is not necessary to file a complete flight plan with the request for clearance, but pilots should state their 

intentions in sufficient detail to permit ATC to fit their flight into the traffic flow. The clearance will not contain 

a specific altitude as the pilot must remain clear of clouds. The controller may require the pilot to fly at or below 

a certain altitude due to other traffic, but the altitude specified will permit flight at or above the minimum safe 

altitude. In addition, at radar locations, flights may be vectored if necessary for control purposes or on pilot 

request. 

NOTE

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The pilot is responsible for obstacle or terrain clearance. 

REFERENCE

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14 CFR Section 91.119, Minimum safe altitudes: General. 

d. 

Special VFR clearances are effective within Class B, Class C, Class D, and Class E surface areas only. ATC 

does not provide separation after an aircraft leaves the Class B, Class C, Class D, or Class E surface area on a 

special VFR clearance. 

e. 

Special VFR operations by fixed

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wing aircraft are prohibited in some Class B and Class C surface areas 

due to the volume of IFR traffic. A list of these Class B and Class C surface areas is contained in 14 CFR Part 91, 

Appendix D, Section 3. They are also depicted on sectional aeronautical charts. 

f. 

ATC provides separation between Special VFR flights and between these flights and other IFR flights. 

g. 

Special VFR operations by fixed

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wing aircraft are prohibited between sunset and sunrise unless the pilot 

is instrument rated and the aircraft is equipped for IFR flight. 

h. 

Pilots arriving or departing an uncontrolled airport that has automated weather broadcast capability 

(ASOS/AWOS) should monitor the broadcast frequency, advise the controller that they have the “one

−

minute 

weather” and state intentions prior to operating within the Class B, Class C, Class D, or Class E surface areas. 

REFERENCE

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Pilot/Controller Glossary Term

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 One

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minute Weather. 

4

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4

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7.  Pilot Responsibility upon Clearance Issuance 

a.  Record ATC clearance. 

When conducting an IFR operation, make a written record of your clearance. The 

specified conditions which are a part of your air traffic clearance may be somewhat different from those included 

in your flight plan. Additionally, ATC may find it necessary to ADD conditions, such as particular departure 

route. The very fact that ATC specifies different or additional conditions means that other aircraft are involved 

in the traffic situation. 

b.  ATC Clearance/Instruction Readback. 

Pilots of airborne aircraft should read back 

those parts

 of ATC 

clearances and instructions containing altitude assignments, vectors, or runway assignments as a means of 

mutual verification. The read back of the “numbers” serves as a double check between pilots and controllers and 

reduces the kinds of communications errors that occur when a number is either “misheard” or is incorrect. 

1. 

Include the aircraft identification in all readbacks and acknowledgments. This aids controllers in 

determining that the correct aircraft received the clearance or instruction. The requirement to include aircraft 

4

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4

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4 

ATC Clearances and Aircraft Separation