Safety Advisory Notice SAN19980042

Safety Advisory Notice issued to: Airservices Australia

Recommendation details
Output No: SAN19980042
Date issued: 08 April 1998
Safety action status: Closed


A flight plan was submitted for an instrument fight rules flight with a planned level of 7,000 ft. The pilot was subsequently cleared to climb to an amended level of 6,000 ft. The amended level, the departure time and the transponder code were reported to the appropriate sector controller. The sector controller read back 7,000 ft. However, the tower controller did not detect the incorrect read-back. Following departure, the pilot reported maintaining 6,000 ft to the sector controller.

The investigation found that while there was a requirement for the controller to use the term "amended" when advising the pilot of the change in the cleared level, there was no similar requirement to use "amended" in air traffic services' (ATS's) coordination procedures.


The instructions in the Manual of Air Traffic Services (MATS) for the application of the word "amended", in both ATS radiotelephony and the exchange of information (coordination), are inconsistent and require clarification.

Manual of Air Traffic Services references

MATS 12-A-20 Clearances and Read Backs, paragraph 4, requires pilots to read back any amendments to an air traffic control route clearance.

MATS 12-A-20 Amended Route or Level, paragraph 1, states: "Whenever it is necessary to assign an aircraft a route or level other than that expected according to the flight plan and any subsequent revisions requested by the pilot, ATS should prefix the route or level information with the term "amended" to alert the pilot that the information and clearance is other than may be expected".

MATS 11-1-2, paragraph 21, details the response required by ATS personnel for messages passed over a fixed service channel (voice). It states that they shall acknowledge a message with any item notified in the clearance as "amended or recleared".

MATS 2-5-1, paragraph 13, requires amended flight plan details for military low jet route aircraft to be clearly labelled "amend details".

MATS 5-1-5, paragraph 66, requires a controller to specify that a route is "amended" when a departure route clearance is amended to include points not flight-planned.


It would appear from the above references that there is an intent to use "amended" as a cue to both pilots and ATS personnel during ground-air and ATS voice coordination communication, whenever some aspect of an original plan or previously advised clearance has changed. However, the procedures for the use of "amended" are not consistent in MATS.

The use of "amended" is not mandatory (but is recommended) in MATS 12-A-20 Amended Route or Level, paragraph 1, yet MATS 12-A-20 Clearances and Read Backs, paragraph 4, requires the pilot to read back any amendments to a clearance. Some discretion is available to ATS personnel if the use of "amended" is only recommended. This can lead to inconsistencies in the application of the term. Consequently, some pilots will receive the cue while others may not.

A similar inconsistency applies in relation to the use of "amended" by ATS personnel during voice coordination communication. MATS 11-1-2, paragraph 21, requires an acknowledgment of any item notified as "amended" or "recleared". However, there is no guidance regarding which items shall be prefixed with "amended".

The procedures for the use of "amended" between ATS personnel in voice coordination communication and between ATS personnel and pilots, should be applied consistently. The application of the same procedures during both coordination and radiotelephony, would minimise doubts regarding the use of "amended" and its meaning. Additionally, as "amended" is not listed in the MATS 12-A-24 Standard Words and Phrases, the inclusion of a definition may be warranted following any review.

Output text

Airservices Australia should note the safety deficiency identified in this report and take appropriate action.

Initial response
Date issued: 14 May 1998
Response from: AirServices Australia
Response text:

Use of the term "amended" in co-ordination and R/T procedures.

The non use the term "amended" in the subject occurrence (9702674) was not consistent with the directives of MATS and may have contributed to the missed incorrect readback.

Your comments with regard to MATS, and clearance items which are amended, are noted, and have been referred to Operational Policy Branch for attention.

Last update 01 April 2011