Operations resources


Controlled airspace


This section sets out pilot actions and related ATS activity in civil and military controlled airspace.

Airspace classification


Class of airspace operations and services AIP ENR 1.4

Class C
Controlled airspace at and below FL285 excluding airspace designated as Class D or Class E
Class D
IFR and VFR flights are permitted and all flights are subject to ATC clearance
IFR flights are separated from other IFR flights
IFR flights receive a separation service in respect of other VFR flights
A separation service is a controlled condition whereby a separation standard need not be applied between IFR and VFR aircraft.
Class E
IFR and VFR flights are permitted
IFR flights are subject to ATC clearance
IFR flights are separated from other IFR flights
IFR flights receive traffic information on known VFR flights as far as practicable
Class G
IFR and VFR flights are permitted and receive flight information service if requested
Non-controlled airspace

For flight in close proximity to the boundary of controlled airspace, separation is not provided with traffic operating outside controlled airspace.

General AIP ENR 1.1

Except in an emergency, a clearance is required for all flights in Classes A, C, and D airspace, restricted areas and for IFR flights in Class E airspace, except when operating in accordance with IFR pick-up procedures.

Clearance is not required for VFR flights in Class E airspace.

Special requirements apply to parachute jumping operations (ENR 5.5).

For entry into Class D airspace, establishment of two-way communications between the aircraft and ATC constitutes a clearance for the pilot to enter Class D airspace (ENR 1.1).

Where the airspace classification and flight rules require, an aircraft must not enter controlled airspace without a clearance (see page 3.78 for holding procedures). The pilot is responsible for obtaining a clearance and, once obtained, must not amend a planned route, deviate from the cleared track, or change level without obtaining ATC approval. When determining where the clearance request will be made, the pilot should consider:

  • aircraft performance
  • the possibility of frequency congestion if the airspace is known to be busy
  • the possibility of changes to route and/or level
  • the possible delays that might be incurred when clearances have to be coordinated with adjacent ATC sectors.

Completed deviations from cleared route

When clearance has been issued to deviate from a cleared route, the pilot must advise ATC when the weather deviation is no longer required, or when the weather deviation has been completed and the aircraft has returned to its cleared route. Further deviations from route will require a new clearance.

Clearances for entry into CTA

All flights operating in Class E or G airspace requesting a clearance to operate in Class C or D airspace must advise position, level and tracking details when making first contact with ATC.

Within VHF radio coverage, pilots must maintain continuous communications with ATC when operating in Class C and D airspace. Further, when in Class E airspace, pilots of VFR flights should monitor the ATS frequency appropriate to their area of operation.

When communication facilities permit, ATC will pass clearances direct.

The clearance authorises flight in the specified manner to the first point at which the flight leaves controlled airspace, or, if completely in controlled airspace, to the first landing point.

Clearances provided to pilots may include a “CLEARANCE VOID TIME’. A clearance is only valid if the flight enters controlled airspace in accordance with the clearance at or before that time.

Clearance amendents

An air traffic clearance proposed by ATC does not relieve the pilot from complying with statutory requirements, nor from responsibility for the ultimate safety of the aircraft.

If considered necessary, a pilot should request a different clearance from that issued. In an emergency, a pilot may act without a clearance and immediately advise ATC.

A pilot must advise ATC immediately if issued a clearance which requires the use of navigation aids not available to the aircraft, or that the pilot is not qualified to use.

ATC is responsible for issuing clearances that will enable an aircraft to remain within controlled airspace if the pilot has planned to do so. If a pilot is in doubt that the clearance will keep the aircraft in controlled airspace, ATC should be advised and an alternative clearance may be requested.

For operations within Class C, D or E airspace, maintaining 500 ft above the lower limit of the CTA steps will provide a vertical buffer with aircraft operating in the adjoining airspace.

A control instruction issued after a clearance is obtained amends the appropriate item in the clearance. When there is any change in the clearance limit and/or route specified in the initial clearance, a completely new clearance will be issued.

Whenever a restriction or requirement has been imposed, and a further restriction/requirement is subsequently imposed, the subsequent instruction will cancel all previous restrictions/requirements unless:

  • all restrictions/requirements are restated, or
  • the subsequent instructions is prefixed ‘Further requirement’.

At a controlled aerodrome, clearance for operation in an adjoining control area is given before departure.

If proposing to fly into a control area from an aerodrome located so close to the entry point that making a full position report before entry is not practicable, a clearance should be requested:

  • at a convenient time before entering the runway for take-off at an aerodrome where communication can readily be established before take-off, or
  • after take-off, if not available or obtainable before take-off, provided that the aircraft does not enter the control area until cleared.

If landing at an aerodrome with the intention of departing for a control area shortly after landing, any revision of notified details relevant to the clearance, including EOBT, should be advised to ATC, and a clearance requested before landing.

Clearances provided to pilots may include a ‘clearance void time’. Where a void time is specified, the clearance is valid only if the flight enters controlled airspace in accordance with the clearance at or before that time.

Pilots should submit details required for flight in controlled airspace at least 30 minutes before the expected time of entry. Flight details submitted with less than 30 minutes notification will be processed on a ‘controller workload permitting’ basis, and may be subject to delay

Within a Class D CTR, a clearance to take off is a clearance to operate within the CTR.

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New rules come into effect from 2 December 2021 that cover the general operating and flight rules. We are currently updating this guide to reflect the new rules. A new version will be available to download from 2 December.
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