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
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
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
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
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
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.