Jump to Content

Safety Action


Australian Transport Safety Bureau (ATSB) Safety Action

As a result of the investigation, the Australian Transport Safety Bureau issues the following recommendations:

Recommendation R20030056

The Australian Transport Safety Bureau recommends that Airservices Australia conduct a review to determine why flight crews were able to submit flight plans and operate on non-standard routes in contravention of the AIP, which required crews to plan on routes provided to the air traffic control system by the publication of air route specifications.

Recommendation R20030057

The Australian Transport Safety Bureau recommends that Airservices Australia conduct a review to establish the extent of the use of non-standard levels in situations initiated by pilots and in situations initiated by controllers.

Recommendation R20030058

The Australian Transport Safety Bureau recommends that the Civil Aviation Safety Authority review the Table of Cruising Levels in AIP and its continuing relevance.


The following extracts are taken from Bureau investigations completed since 1997. They are provided as an indication of where the use of a non-standard level was a factor in selected occurrences and do not attempt to provide all the factors involved in those investigations. Full reports of these occurrences are available from the ATSB on request.


The westbound A320, VH-HYA, was maintaining a non-standard flight level (FL370) which resulted in an eastbound A320, VH-HYR, being given a non-standard level (FL350) for the initial level clearance. This consequential action had the effect of placing VH-HYR in direct conflict with the 737. Had standard levels been applied on the two-way route system that was under procedural control, a safety net would have been put in place. This net would have become prominent had the Perth controller not observed the radar paint of the 737.


The approval for the B767 to operate at a non-standard level for the track flown cancelled the defence normally provided to the air traffic system by the use of standard levels.


The controller stated that although he had acknowledged that CZA was at FL370, he was not fully aware that the aircraft was at a non-standard level. He was concentrating on the voice switching and communication system and the potential problems for sequencing aircraft that were soon to enter his airspace.

The controller stated that had allowed his "scan" to be diverted and, when the short-term conflict alert activated, he knew immediately what the problem was and acted to rectify the infringement of separation standards. He was unable to explain either his poor task prioritisation or his memory lapse.


The crew of the 737 was recleared from a standard level to a non-standard level and, in order to provide track shortening, from a track that would have provided separation with the B767, to one that conflicted with the B767. The allocation of a non-standard flight level on a one-way route does not guarantee separation from opposite traffic on other, crossing, one-way routes. However, the planned routes of these two aircraft did not cross and were laterally separated. The conflict would have been avoided had the 737 continued on its planned route or had it maintained a standard level.


Separation assurance with the northbound Dash 8 was lost when the crew of the southbound Dash 8 was assigned a non-standard flight level. The conflict would have been avoided had a standard level been assigned.

Share this page Comment