Entering Controlled Airspace

Entering Controlled Airspace

Infringement of controlled airspacedanger and restricted areas and prohibited areas is a serious aviation hazard and occurs when an aircraft enters such airspace without necessary permission.

A significant cause of airspace infringement is that some pilots are not familiar with the correct procedure for entering controlled airspace and do so without clearance. This article deals with international regulations concerning entering controlled airspace.

National regulations may differ in detail but will follow the same general rules.

ICAO Annex 2: Rules of the Air

The Rules of the Air state that clearance must be obtained before an aircraft enters controlled airspace (with the exception of a VFR aircraft entering class "E" airspace). All aircraft wishing to enter controlled airspace must file a flight plan, either on the ground before flight, or in the air, and the air traffic services involved must receive the request at least 10 minutes before the expected time of entry. (See ICAO Annex 2, Chapter 3, Section 3.3)

Getting clearance may take a little time; the controller has other jobs to do and may be dealing with a more urgent task - perhaps on another frequency, and he/she has to check the position and level of other aircraft before giving clearance. That is why the request must be made at least 10 minutes before entry time.

  • An aircraft must not enter controlled airspace until clearance has been received.
  • It is not sufficient that the pilot has informed the controller of his/her request; entry must await receipt of formal clearance;
  • The aircraft must stay clear of controlled airspace while awaiting clearance.

How to Ask for Clearance

A pilot wishing to enter controlled airspace should call the ACC responsible for the controlled airspace concerned using the frequency specified in the AIPs or Flight Information Publication.

The initial call should be made at least 10 minutes before the point of entry, and should consist of the aircraft call sign followed by a brief statement of the request.

“Zenda Control ABCDE, request crossing of A1 at Benton”.

The controller will reply, saying either:

“ABCDE, Zenda Control, Standby”, or

“ABCDE, Zenda Control, pass your message”.

If the reply was “Standby”, then clearance has not been given and the aircraft must wait, keeping out of controlled airspace.

If the reply was “pass your message”, then the following information should be passed:

  • aircraft call sign and type,
  • position,
  • heading,
  • present level,
  • flight conditions,
  • crossing position,
  • requested crossing level, and,
  • estimated time at the crossing position.

“Zenda Control ABCDE is a Cessna 172, 25 miles West of Benton heading 100, FL 70 VMC, request crossing clearance of airway A1 at Benton FL 70 at 1023.”

Clearance may not be granted straight away, because the controller has to check the position and levels of other traffic. Until clearance is received, the aircraft must stay clear of controlled airspace.

When the controller passes the crossing clearance, the pilot must read it back so that he/she can check that it has been copied correctly.

The clearance may not be exactly the same as was requested, but it must be obeyed. For example, if the clearance was at a different flight level from that requested, the aircraft must climb or descend to the cleared level before entering controlled airspace. If the pilot is unable to comply with the clearance (e.g. if doing this will cause a VFR flight to enter IMC or due to the aircraft being unable to climb), they must advise the controller and receive an alternative clearance. The aircraft must remain outside controlled airspace until the process is complete.

Accidents and Incidents

This section contains events where aircraft entered controlled airspace without obtaining ATC clearance.

Further Reading


  • ICAO Annex 2: Rules of the Air, Chapter 3, Section 3.3;

EUROCONTROL Airspace Infringement Initiative

EUROCONTROL Guidance Notes for GA pilots

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