This consultation proposed amendments to the Part 121 Manual of Standards (MOS) to replace expiring provisions, amend alternate aerodrome planning requirements and TAWS definitions in the rules.

Key changes proposed were:

• Maintaining a consistent approach to aviation rescue and firefighting services (ARFFS) at Australian aerodromes - the requirement for ARFFS to be planned at extended diversion time operations (EDTO) en-route alternate aerodromes will not be introduced.
• Replacing transitional RNP-based engine-out departure procedure (EODP) obstacle assessment area (OAA) requirements for operators with highly capable aeroplanes.
• Permitting reduced pre-flight destination aerodrome wet or contaminated pre-flight landing performance where an alternate aerodrome is planned.
• Limiting alternate aerodrome minima to be no higher than destination aerodrome minima.
• Improving alternate aerodrome minima requirements by adding an extra item to the alternate aerodrome minima table.
• Allowing isolated destination aerodromes to be planned to have a destination alternate aerodrome.
• Aligning instrument approach classifications to reflect updated Part 91 MOS changes.
• Amending the definition of TAWS Class-A and TAWS Class-B to permit an earlier version of the technical specification.

About this consultation

The consultation opened on 13 October 2025 and closed 10 November 2025.

A summary of the feedback is provided below.

Prior to the release of this consultation, CASA consulted internally as well as externally via the Aviation Safety Advisory Panel (ASAP) and the Part 121 Technical Working Group (TWG), consisting of representatives from CASA and the larger aeroplane air transport sector.

The proposed amendments are also partly in response to industry feedback received by CASA since the commencement of the flight operations regulations in December 2021.

Based on that prior work it was anticipated that the consultation be grouped into 3 broad themes:

• EDTO en-route alternate aerodrome (ERA) requirements, specifically the requirement for Category 4 rescue and firefighting services (RFFS) at ERA aerodromes within Australian territory (Change 1).
• Engine-out departure procedure (EODP) design criteria, which currently rely on expired legacy CAO 20.7.1B-based methods (Change 2).
• Other prescriptive requirements relating to alternate aerodrome planning minima, landing performance on wet or contaminated runways, and isolated destination aerodrome planning. (Changes 3 to 8).

We received 9 responses with 4 respondents consenting to having their submission published.  

The largest group represented 4 Part 121 operators (other than Subpart 121.Z) which included major airlines. One response received was from a Part 135 operator and 4 respondents identified as 'other'.

Among the respondents that are not Part 121 or Part 135 operators, feedback was received from:

• Professional Pilots' Association (Australian Airline Pilots’ Association - AusALPA)
• OEM - Airplane Manufacturer (The Boeing Company)
• ARFFS provider (Airservices Australia).

Summary of feedback

Change 1 - Maintaining a consistent approach to aviation rescue and firefighting services (ARFFS) at Australian aerodromes - the requirement for ARFFS to be planned at extended diversion time operations (EDTO) en-route alternate aerodromes will not be introduced

We received 7 responses to this question.

Three respondents agreed with the proposal. Two respondents disagreed. Both provided extensive comments in support of their rejection of the proposal.

AusALPA reiterated their previous view that CASA should develop a risk-based rule that includes State and Territory fire services. This rule should provide an 'equivalency' of the provision of RFFS, supported by guidance material illustrating how this could be achieved.

The Boeing Company provided comment that CASA should retain the RFFS requirement at EDTO ERA. They also suggested that most large transport airplanes require destination, departure, and alternate airports to be equipped with RFFS commensurate with the size of these airplanes, i.e., higher than RFFS Category 4.

One respondent provided comment supporting the notion that RFFS should be provided where there is significant operational activity.

Two respondents selected Undecided/Not my area of expertise. Two respondents did not answer this question.

In summary, the responses did not reveal any new or different material than had already been received and reviewed in the development of the policy proposal.

Change 2 - Replace transitional RNP-based engine-out departure procedure design (EODP) obstacle assessment area (OAA) requirements for operators with highly capable aeroplanes (also relevant to some Part 135 and CASA EX74/24 operations)

There were 6 responses to this question.

Two respondents agreed with the proposal. One respondent disagreed with the proposal. That respondent provided extensive comments in support of their position. Analysis of those comments indicates that the rejection of the proposal is likely to be a consequence of not fully understanding the proposal.

Three respondents selected Undecided/Not my area of expertise. Three respondents did not answer this question.

In summary, the responses did not reveal any new or different material than had already been received and reviewed in the development of the policy proposal.

Change 3 - Permit reduced pre-flight destination aerodrome wet or contaminated pre-flight landing performance where an alternate aerodrome is planned (also relevant to some Part 135 and CASA EX74/24 operations)

We received 2 responses that agreed to this proposal.

Two respondents selected Undecided/Not my area of expertise, and 5 did not answer this question.

Change 4 - Limit alternate aerodrome minima to be no higher than destination aerodrome minima

We received 4 responses that agreed with the proposal. One of those that agreed also provided a comment in relation to requesting CASA review simplifying the minima calculation.

Three respondents selected Undecided/Not my area of expertise and 2 respondents did not answer this question.

Change 5 - Improving alternate aerodrome minima requirements by adding an extra item to the alternate aerodrome minima table

We received 5 responses that agreed with the proposal. One of those that agreed also provided a comment requesting CASA provide clarification in relation to what level of GNSS equipment satisfies the IAP requirements.

Two respondents selected Undecided/Not my area of expertise and 2 respondents did not answer this question.

Change 6 - Allowing isolated destination aerodromes to be planned to have a destination alternate aerodrome

We received 3 responses that agreed with the proposal.

Two respondents selected Undecided/Not my area of expertise and 3 respondents did not answer this question.

One response disagreed with the proposal where they contend that the same (baseline) destination alternate fuel requirements should prevail irrespective of the diversion distance.

Change 7 - Aligning instrument approach classifications to reflect updated Part 91 MOS changes

We received 6 responses that agreed with the proposal.

One respondent selected Undecided/Not my area of expertise and 2 respondents did not answer this question.

Change 8 - Amend definition of TAWS Class-A and TAWS Class-B to permit an earlier version of the technical specification (relevant to Part 121, 135, 121.Z and CASA EX74/24 operations)

We received 5 responses that agreed with the proposal. One respondent selected Undecided/Not my area of expertise and 3 respondents did not answer this question.

In summary, the responses to changes 3-8 did not reveal any new or different material than had already been received and reviewed in the development of the policy proposal.

Consulted amendments to the Part 121 MOS are now approved and in effect.

They replace expiring provisions, amend alternate aerodrome planning requirements and the terrain awareness and warning system (TAWS) definition.

You can view the amendments on the Federal Register of Legislation.