Air Traffic Controllers FAQ

1. Why did ICAO introduce a more lengthy phraseology?

The new phraseologies were designed by controllers and pilots, just like you. While the phraseologies may seem longer to use, they are meant to allow the controllers' intent to be clearly conveyed to flight crews, with no implied meaning or expectations. There were increasing safety concerns regarding flight crew confusion during the approach and departure phases at various locations, and clear signs that these occurrences will increase as traffic complexity grows. The new phraseology removes ambiguity in ATC clearances issued to flight crews when on SIDs or STARs. 

2. Can I clear an aircraft to fly on a SID or STAR using the instructions CLIMB VIA SID, or DESCEND VIA STAR?

No! You are issuing an incomplete clearance. When using the ICAO SID/STAR procedures, the clearance to climb on the SID or descend on the STAR must include a cleared level. PANS ATM a) and a) refers.


The correct phraseology is CLIMB VIA SID TO (level) or DESCEND VIA STAR TO (level). The guiding principle behind the phraseology is clarity and consistency with no implied expectations. Improper use of the phraseology may confuse flight crews and increase your workload with additional queries.


NOTE: Flight crews may be operating in environments where the use of procedures that differ from those published by ICAO. For example, flight crews operating in the U.S. national airspace system receive clearances to CLIMB VIA SID and/or DESCEND VIA STAR without a cleared level. Controllers should maintain vigilance against errors arising from erronous readbacks from flight crews.

3. When can I issue the clearance to DESCEND TO (level) instead of DESCEND VIA STAR TO (level)?

For an aircraft flying on the SID/STAR, DESCEND TO (level) can be used when there are no remaining published speed or level restrictions on the procedure, or in conjunction with CANCEL SPEED AND LEVEL RESTRICTION(S). DESCEND TO (level) is also used if you have vectored the aircraft off the procedure or have cleared the aircraft to a waypoint that is not on the STAR.


For aircraft on vectors, or otherwise taken off an ATS route or published procedure, DESCEND TO (level) should be used.

4. Do I have to repeat CLIMB VIA SID TO (level) every time I clear the aircraft to a higher level?

For aircraft flying on a SID with remaining published level or speed restrictions you must use the phraseology CLIMB VIA SID TO (level) consistently when issuing level change instructions. This is to ensure that pilots understand their obligation to comply with the published restrictions on the SID/STAR.

NOTE: Please bear in mind that if you find yourself issuing excessive level instructions, the published SID/STAR level restrictions may not reflect ATC operational needs for traffic de-confliction. SID and STARs should be designed to facilitate aircraft in climb or descent through terminal airspace, while complying with speed and level restrictions necessary for air traffic de-confliction and management. The SID/STAR phraseologies allow for a harmonised conveyance of ATC intent and flight crews compliance with the SID/STAR restrictions, which should result in minimised ATC intervention on climb/descend phases, and lesser "active control".

5. If I were to use CLIMB TO (level) while the aircraft is flying on SID with active restrictions, what will the pilot do?

This is an incorrect phraseology to use, since there are remaining active restrictions. The flight crew may wrongly assume that these restrictions are cancelled, since the phraseology CLIMB TO (level) is used when there are no remaining restrictions. This wrong use of phraseology may result in flight crew confusion, level busts, and possible loss of separation.


Moreover, the use of incorrect phraseology will create uncertainty for flight crews, and the questions to clarify the clearance creates unnecessary workload and RT for ATCOs.

If you intend to cancel both speed and level restrictions up till the cleared level, it must be explicitly stated. The proper phraseology for such cancellation is:

      1. CLIMB UNRESTRICTED TO (level), or


6. Do I have to reiterate the cleared level when I vector an aircraft off the SID/STAR or clear the aircraft direct to a waypoint not on the SID/STAR?

Yes. The cleared level needs to be restated at least once when the pilot is given an instruction that takes the aircraft off the SID/STAR. This requirement also applies when the aircraft is issued a clearance to rejoin the SID/STAR.

7. Is the STAR cancelled when the aircraft is cleared direct to a fix along the STAR?

No, issuing a CLEARED DIRECT clearance for a waypoint on the STAR means the aircraft will resume its navigation on the STAR at the cleared waypoint. The aircraft is no longer on the lateral profile of STAR, and the restrictions of the bypassed waypoints are cancelled. The pilot will then rejoin the STAR at the given waypoint and comply with all restrictions henceforth.

However, please note that if the aircraft was cleared direct to a waypoint not on the STAR, the STAR is no longer applicable, and the aircraft is now in a situation similar to that of being vectored by ATC. 

8. When the aircraft is cleared direct to a point on a SID or STAR, who becomes responsible for terrain clearance?

When an aircraft is issued a CLEARED DIRECT clearance, ATC becomes responsible for ensuring that the prescribed obstacle clearance exists until the aircraft reaches the point as cleared.

During this segment of the flight, the correct descent clearance is DESCEND TO (level).

9. When I cancel restrictions(s) at the waypoint(s) (e.g. speed and/or level) on the SID or STAR, does it mean the pilot can maintain any level or speed?

The aircraft should continue to climb/descend to maintain the cleared level as instructed. Any cancellation of level restriction(s) does not change their obligation to meet the cleared level, it only affects how the aircraft may adjusts it's vertical profile to meet the clearance.


When cancelling the speed restrictions on SIDs or STARs, the speed restrictions associated with various classes of airspace (Annex 11, Appendix 4) remain valid, as would any other imposed restrictions not associated with the procedure.   

10. When I take an aircraft off a SID/STAR, with the intention of subsequently returning the flight to the procedure, must I advise the pilot as such? Are there additional requirements in that situation?

PANS-ATM, requires the controller to notify the pilot if it is expected that the aircraft will be subsequently instructed to rejoin the SID/STAR, and the waypoint to join the procedure. Flight crews will retain the procedure in their flight management system (FMS) and may be better positioned to advise the controller if they are unable (e.g. due weather) to rejoin at the expected waypoint. This allows for better flight and traffic management for flight crews and ATC.

When subsequently clearing the aircraft back to the SID/STAR, ATC should ensure that aircraft is correctly positioned (speed, level ,etc) to rejoin the procedure and comply with the associated restrictions thereafter.

If there were no prior notification given, when the aircraft is subsequently told to REJOIN the SID/STAR, the designator of the SID/STAR shall be included in the clearance. PANS-ATM a) refers.

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