Part 121 (Australian Air Transport Operations—Larger Aeroplanes) Amendment Manual of Standards 2025

Explanatory Statement

Civil Aviation Safety Regulations 1998

Part 121 (Australian Air Transport Operations—Larger Aeroplanes) Amendment Manual of Standards 2025

Purpose

The instrument amends the Part 121 (Australian Air Transport Operations—Larger Aeroplanes) Manual of Standards 2020 (the Part 121 MOS), which sets out the standards for the operation of larger aeroplanes for an Australian air transport operation.

The instrument includes amendments that address transitional provisions in the Part 121 MOS introduced at commencement in December 2021 to support industry transition from legacy Civil Aviation Orders (CAOs) and the Civil Aviation Regulations 1988 (CAR) that previously contained the flight operations rules to the new flight operations regulations (comprising Parts 119, 121, 133 and 135 of the Civil Aviation Safety Regulations 1998 (CASR)). Transitional arrangements included a requirement (due to have commenced on 2 December 2025) for category 4 rescue and firefighting services (RFFS) capability to apply for en-route alternate aerodromes (ERA) used for extended diversion time operations (EDTO). The instrument repeals the proposed requirement, to avoid unintended consequences relating to the proposed standard at paragraph 4.19(2)(d) of the Part 121 MOS, such as limiting EDTO or requiring costly infrastructure upgrades at remote aerodromes.

The instrument provides an enduring alternative method to comply with performance rules regarding engine-out departure procedures (EODPs), to replace the alternative method set out in subsection 12A of Civil Aviation Order 20.7.1B (CAO 20.7.1B), that had been incorporated into the Part 121 MOS (incorporation of which expires at the end of 1 December 2025). Broadly, the changes are expected to improve operational efficiency by enabling higher dispatch weights, reduced fuel burn, and lower emissions. This will enable operational flexibility while preserving safety through alternative controls (e.g. requiring operator approvals, and the use of accredited procedure designers). It is expected that the amendments would encourage adoption of advanced navigation capabilities (e.g. required navigation performance authorisation required departure (RNP AR DP)) and modern safety systems (e.g. TAWS-Class A, being a type of terrain awareness and warning system), enhancing long‑term safety performance.

The instrument amends a number of prescriptive requirements relating to alternate aerodrome planning minima, landing performance on wet or contaminated runways, and isolated destination aerodrome planning. The changes regarding destination isolation aerodromes are expected to support regional and remote connectivity, by permitting flights to isolated aerodromes under specified conditions, and reducing the likelihood of service cancellations.

Other minor or technical amendments align definitions of instrument approach procedures with changes recently made to the Part 91 MOS, and otherwise correct editorial errors or clarify the intention of provisions.

Overall, the amendments represent a continuation of existing policy settings with targeted refinements to align with contemporary operational practices and international standards.

Legislation

Section 98 of the Civil Aviation Act 1988 (the Act) empowers the Governor-General to make regulations for the Act and in the interests of the safety of air navigation. Relevantly, the Governor-General has made CASR and CAR.

For the alternative required navigation performance (RNP)-based EODPs, new subsection 9.04A(2) of the Part 121 MOS requires that the operator of the aeroplane be the holder of an approval under regulation 91.045 of CASR to use a navigation specification of RNP AR DP, issued for the purposes of subparagraph 91.660(1)(b)(i) of CASR (or equivalent foreign issued approval).

Also, under new subsection 9.04A(3) of the Part 121 MOS, the alternative RNP-based departure procedures can be used only if the designer of the procedure holds a procedure design certificate or a procedure design authorisation, in force under Part 173 of CASR (or equivalent authorisation issued by the Federal Aviation Administration of the United States of America (FAA), the European Aviation Safety Authority (EASA), or the national aviation authority of the United Kingdom, New Zealand or Canada).

Under regulation 11.015 of CASR, an approval or authorisation granted under the Australian jurisdiction is an authorisation under Part 11 of CASR, with Subpart 11.BA of CASR applying to the authorisation.

Regulation 11.055 of CASR sets out criteria that apply to the Civil Aviation Safety Authority (CASA) when granting an authorisation. Regulation 11.056 provides that an authorisation may be granted subject to any condition that CASA is satisfied is necessary in the interests of the safety of air navigation. Under regulation 11.077, a person commits an offence of strict liability (with a maximum penalty of 50 penalty units) if the person breaches a condition of an authorisation.

Under regulation 121.015 of CASR, CASA may issue a Manual of Standards (MOS) for Part 121 of CASR that prescribes matters required or permitted by that Part to be prescribed, or necessary or convenient for carrying out or giving effect to Part 121 of CASR. This power is complemented by other provisions, throughout Part 121 of CASR, which empower CASA to prescribe specific matters in the MOS.

Under subregulation 121.170(1) of CASR, the Part 121 MOS may prescribe requirements relating to flight preparation and alternate aerodromes. Under subregulations 121.170(2) and (3), it is a strict liability offence (with a maximum penalty of 50 penalty units) by the operator and pilot in command of an aeroplane for a flight if such a requirement is not met for the flight. Chapter 4 of the Part 121 MOS is made for subregulation 121.170(1) and prescribes requirements relating to flight preparation and alternate aerodromes.

Under subregulation 121.235(1) of CASR, the Part 121 MOS may prescribe requirements relating to fuel for aeroplanes. Under subregulations 121.235(2) to (4), it is a strict liability offence (with a maximum penalty of 50 penalty units) by the operator and pilot in command of an aeroplane for a flight if they are subject to such a requirement and the requirement is not met for the flight. Chapter 7 of the Part 121 MOS is made for subregulation 121.235(1) and prescribes requirements relating to fuel for aeroplanes.

Under subregulation 121.395(1) of CASR, the Part 121 MOS may prescribe requirements relating to take-off performance for a flight of an aeroplane. Under subregulations 121.395(3) to (5), it is a strict liability offence (with a maximum penalty of 50 penalty units) by the operator or pilot in command of an aeroplane for a flight if they are subject to such a requirement and the requirement is not met for the flight. Chapter 9 of the Part 121 MOS is made for subregulation 121.395(1) and prescribes requirements relating to take-off performance for a flight of an aeroplane.

Under subregulation 121.460(1) of CASR, the Part 121 MOS may prescribe requirements relating to the fitment and non-fitment of equipment to an aeroplane, the carrying of equipment on an aeroplane, and equipment that is fitted to, or carried on, an aeroplane. Under subregulations 121.460(2) and (3), it is a strict liability offence (with a maximum penalty of 50 penalty units) if a person is subject to such a requirement and the requirement is not met. Chapter 11 of the Part 121 MOS is made for subregulation 121.460(1) and prescribes requirements relating to equipment.

Under subsection 14(1) of the Legislation Act 2003 (the LA), a legislative instrument may make provision in relation to matters by applying, adopting or incorporating provisions of an Act or disallowable legislative instrument as in force at a particular time or as in force from time to time. A legislative instrument may also make provision in relation to matters by applying, adopting or incorporating any matter contained in any other instrument or writing as in force at, or before, the time the legislative instrument commences. Under subsection 14(2) of the LA, unless the contrary intention appears, the legislative instrument may not make provision in relation to a matter by applying, adopting or incorporating any matter contained in an instrument or other writing as in force or existing from time to time. However, subsection 98(5D) of the Act provides that, despite section 14 of the LA, a legislative instrument made under the Act or the regulations may apply, adopt or incorporate any matter contained in any instrument or other writing as in force or existing from time to time, even if the other instrument or writing does not yet exist when the legislative instrument is made.

Under subsection 33(3) of the Acts Interpretation Act 1901, where an Act confers a power to make, grant or issue any instrument of a legislative or administrative character (including rules, regulations or by-laws), the power shall be construed as including a power exercisable in the like manner and subject to the like conditions (if any) to repeal, rescind, revoke, amend, or vary any such instrument. Under subsection 13(1) of the LA, subsection 33(3) applies to legislative instruments as if each provision of the instrument were a section of an Act.

Background

The Part 121 MOS sets out the standards for the operational, procedural and safety risk management standards for the conduct of Australian air transport operations in larger aeroplanes. The MOS consolidated the existing rules of the air and contained some new rules to enhance operational flexibility, improve aviation safety and bring Australian requirements more in line with the Standards and Recommended Practices (SARPs) of the International Civil Aviation Organization (ICAO).

To support industry transition for new rules, CASA implemented transitional arrangements in the Part 121 MOS and further in CASA EX161/21 — Miscellaneous Flight Operations Exemptions and Approvals (Transitional) Instrument 2021. The requirement in paragraph 4.19(2)(d) of the Part 121 MOS for category 4 RFFS capability (under the Part 139H MOS) at ERA for EDTO had a delayed commencement that was extended twice for the purpose of holding policy discussions. The old regime for alternative EODP design criteria, incorporated into the MOS from subsection 12A of CAO 20.7.1B as in force immediately before the commencement of the Part 121 MOS (2 December 2021) had a self‑repeal date of 2 December 2025.

The Part 121 Aviation Safety Advisory Panel (ASAP) Technical Working Group (TWG) has played a key role in shaping the Part 121 MOS provisions, particularly in 2020 and again in December 2024, when members provided feedback on the EDTO en-route aerodrome RFFS requirement and the EODP design criteria.

Since commencement of the Part 121 MOS, in addition to the matters mentioned in the preceding 2 paragraphs, CASA has received industry feedback, including individual exemption applications and industry queries. These highlighted operational challenges and prompted CASA to consider more enduring legislative solutions.

In consequence, CASA has developed the measures in this instrument regarding reduced landing performance margins, alternate aerodrome minima, planning a destination alternate aerodrome for isolated aerodrome destinations and TAWS-Class A technical standards.

Overview of instrument

In accordance with subsection 33(3) of the Acts Interpretation Act 1901, the instrument makes amendments to the Part 121 MOS.

In broad terms, the amendments to the Part 121 MOS deal with some expiring transitional provisions and introduce refinements that maintain an equivalent level of safety while improving operational flexibility and reducing compliance costs.

The proposed requirement for category 4 RFFS at ERA within Australian territory for EDTO is removed. This alleviation reflects infrastructure limitations and the very low likelihood of diversion to these aerodromes. Operators will continue to comply with other EDTO safety requirements.

The amendments also replace the transitional EODP design criteria (which incorporated provisions from CAO 20.7.1B) with contemporary RNP-based design criteria, including updated obstacle assessment parameters and mandatory use of accredited instrument flight procedure designers. Operators must hold RNP AR DP approvals to use these procedures, ensuring competency and safety.

The instrument alleviates the landing performance requirements for wet or contaminated runways. Operators may now dispatch aeroplanes to destination aerodromes forecast to be wet or contaminated at higher weights, provided a compliant destination alternate aerodrome is planned. This change introduces operational flexibility while maintaining safety with the use of additional planning controls.

The instrument provides for alternate aerodrome minima to be no more restrictive than destination minima and permit isolated destination aerodromes to be planned with an alternate aerodrome under enhanced fuel requirements.

The instrument also provides for updates to the terminology used for instrument approach procedure classifications that were recently introduced into the Part 91 MOS. These now align with the new definitions APV, NPA, PA.

The terrain and warning system (TAWS) definitions are amended to allow use of equipment that meets (E)TSO-C151a and subsequent versions. This allows the use of equipment meeting earlier standards, which CASA assessed as having no detriment to the safety of air navigation.

CASA has assessed the impact of these amendments on aviation safety in accordance with section 9A of the Act. The proposed changes maintain an equivalent level of safety to existing provisions by introducing alternative safety controls where prescriptive requirements are alleviated. These controls include operator approvals, accredited procedure designers and enhanced planning requirements. CASA considers the amendments necessary and appropriate to ensure safe, efficient and cost-effective operations while supporting continued service to regional and remote communities.

Documents incorporated by reference

In accordance with paragraph 15J(2)(c) of the LA, the following table contains a description of the documents incorporated by reference into the legislative instrument, the organisation responsible for each document and how they may be obtained. The table also states how the document is incorporated.

Content of instrument

Section 1

Section 1 provides that the instrument is the Part 121 (Australian Air Transport Operations—Larger Aeroplanes) Amendment Manual of Standards 2025.

Section 2

Section 2 provides that the instrument commences at the time that it is registered.

Section 3

Section 3 provides that the authority of the instrument is CASR.

Section 4

Section 4 provides that Schedule 1 amends the Part 121 MOS.

Schedule 1

Item [1]

This item inserts into the general definitions section terms and expressions to support the amendments, including the definitions related to approach procedures that align with definitions in the Part 91 MOS, for the purposes of section 4.11.

Items [2] and [3]

The amendments made by these items correct and clarify the intended operation of subsection 4.08(1).

Item [4]

This amendment corrects a cross-reference in subsection 4.10(3).

Items [5] and [6]

The amendments clarify the operation of paragraph 4.10(3)(b).

Item [7]

The amendment makes a grammatical correction.

Item [8]

This item inserts table item 2A into table 4.11. This sets out the criteria for determining whether an aerodrome can be used as a destination alternate aerodrome, an en-route alternate aerodrome or an isolated destination aerodrome. It introduces an additional planning option for aerodromes that have at least 2 operational authorised instrument approach procedures (IAPs), each providing a straight-in approach to a single runway. Under this item, operators would not need to apply the current circling minima additives (400 ft and 1.5 km) when such dual straight-in approach capability exists.

Instead, the planning minima would be based on the second-lowest IAP minima plus specified additives, reducing unnecessary conservatism where redundancy in approach capability is available. CASA assessed that while this amendment represents a minor reduction in ceiling and visibility minima additives compared to existing requirements, the level of safety remains acceptable. This is because the additional item applies only where aerodrome approach infrastructure provides enhanced redundancy and reliability, mitigating risks associated with runway availability and forecast variability.

Item [9]

The item inserts new subsection 4.11(3). This provision ensures the ceiling and visibility minima that apply for the planning of a destination alternate aerodrome, an ERA or an isolated destination aerodrome do not exceed the minima that would apply if those aerodrome types were planned as a destination aerodrome without a destination alternate.

This prevents unintended operational penalties where alternate aerodrome requirements become disproportionately restrictive compared to destination aerodrome requirements. For example, under current rules, an aerodrome with multiple straight-in instrument approaches may still be treated as a single-runway aerodrome for alternate planning, triggering higher ceiling and visibility additives (e.g. 400 ft and 1.5 km). Capping these values avoids unnecessary conservatism while maintaining safety.

The change aligns alternate aerodrome planning with the operational reality that the alternate aerodrome is a contingency option, not the primary landing point, and should not impose stricter requirements than those applied to the destination aerodrome. CASA has assessed that this amendment maintains an equivalent level of safety by preserving the principle that 2 safe landing options must be available while removing unnecessary operational constraints. The adjustment is consistent with ICAO principles and CASA’s risk-based approach to alternate aerodrome planning.

Item [10]

This amendment clarifies the application provision in relation to the requirements in section 4.12.

Item [11]

The item amends subsection 4.12(1) to provide for an exception to the requirements in subsections 4.12(2) and (3) that apply to flights to planned destination aerodromes that are isolated destination aerodromes. The amendment supports item [14].

Items [12] and [13]

These amendments relocate the note about the definition of critical point to below the relevant subsection.

Item [14]

The item inserts subsection 4.12(6). This provision provides an exception to the isolated destination aerodrome requirements that permits operators to plan flights to an aerodrome classified as an isolated destination aerodrome with a destination alternate aerodrome, subject to specific conditions and safety controls.

Under existing provisions, flights to isolated destination aerodromes are an alleviation from the requirement to retain 2 safe landing options, provided sufficient fuel is carried to allow at least 90 minutes endurance after arrival overhead the aerodrome (plus fixed reserves). It requires that the destination aerodrome weather forecast is assessed at the critical point and exceeds the minima specified in table 4.11.

The amendment allows operators to plan flights to isolated destination aerodromes with a destination alternate aerodrome, provided a fully compliant destination alternate aerodrome is planned in accordance with section 4.11, including table 4.11. Fuel planning must also comply with amended section 7.05, which requires that sufficient fuel is carried to mitigate risks associated with extended diversion distances and potential engine failure or depressurisation during diversion.

The amendment preserves the target level of safety by ensuring that 2 safe landing options are retained throughout the flight. Enhanced fuel requirements and alternate aerodrome planning mitigate risks associated with extended diversions and unforeseen operational circumstances. CASA has assessed that this amendment maintains an equivalent level of safety while improving operational flexibility and commercial certainty for flights to remote destinations.

Item [15]

This item repeals paragraph 4.19(2)(d) which, from 2 December 2025, would have introduced the new standard that any en-route alternate aerodrome within Australian territory planned for use during an extended diversion time operation with a maximum diversion time of 180 minutes or less must have:

(a) RFFS to at least MOS Part 139H category 4; or

(b) equivalent facilities available within 30 minutes’ notice.

As a result, the status quo will continue. Operators will not be required to select EDTO ERA within Australian territory based on RFFS capability. This amendment reflects the practical reality that many aerodromes used for domestic EDTO do not have RFFS facilities and imposing this requirement would significantly restrict route planning and increase operational costs. The amendment also avoids unintended consequences such as forcing operators to dispatch flights non-EDTO or cancel services to remote destinations.

CASA has assessed that removing this requirement does not reduce the acceptable level of safety. The likelihood of diversion to an en-route alternate aerodrome is very low, and the absence of RFFS at many departure and destination aerodromes demonstrates that the requirement was aspirational rather than essential for safety. Removing the provision aligns with ICAO principles and CASA’s risk-based approach, ensuring that EDTO remain safe and practical without imposing disproportionate infrastructure requirements.

Items [16], [17], [18] and [19]

These items amend Table 4.19. The table specifies the planning minima for ERA used in EDTO. The amendment achieves alignment with changes made to the Part 91 MOS, which was amended in 2025 to update IAP classifications to APV (Approach with Vertical Guidance), NPA (Non-Precision Approach) and PA (Precision Approach).

Also, the current table does not explicitly include RNP AR APCH (required navigation performance authorization required approach) as a permissible IAP type for planning minima at EDTO ERA. The amendment will clarify that RNP AR APCH is acceptable, supporting operators who hold the necessary approvals and use advanced navigation capabilities.

ICAO Annex 6 and related guidance (Doc 9365 and Doc 10085) classify instrument approaches as NPA, APV or PA and require that planning minima for ERA be based on these classifications. Updating table 4.19 ensures compliance with ICAO SARPs.

CASA has assessed that the inclusion of RNP AR APCH and the adoption of updated IAP classifications will not reduce safety. Operators approved for RNP AR APCH meet stringent performance and training requirements that exceed those applicable to other IAP types. The amendment maintains the target level of safety while improving clarity and operational flexibility.

Item [20]

The item amends subsection 7.02(4) which sets out a definition of destination alternate fuel in the case that the planned destination aerodrome is an isolated destination aerodrome. The provision is amended to clarify that it applies in the case that the aeroplane is operated without a destination alternate aerodrome. This amendment is consequential to the new provisions (see item [14]) that now support a destination alternate aerodrome being planned for the flight.

Item [21]

The item inserts new subsection 7.02(5) which sets out a definition of destination alternate fuel that applies in the case that a planned destination aerodrome for a flight of the aeroplane is an isolated destination aerodrome, and a destination alternate aerodrome is planned for the flight.

Where a flight is planned to an aerodrome classified as an isolated destination aerodrome under section 4.03 of the Part 121 MOS, and the operator elects to plan a destination alternate aerodrome, the fuel requirements are amended accordingly.

The amendment to section 7.02 requires that the aircraft must carry, at the missed approach point at the isolated destination aerodrome, sufficient fuel to:

(a) proceed to the planned destination alternate aerodrome; and

(b) fly for 15 minutes at a holding speed at 1 500 feet above the aerodrome elevation in International Standard Atmosphere (ISA) conditions; and

(c) conduct an approach and landing.

This fuel quantity must be calculated based on the greater of the fuel consumption resulting from either:

(a) an engine failure; or

(b) a loss of pressurisation.

The requirement reinstates the fuel planning obligations that would otherwise be alleviated under the isolated destination aerodrome provisions, ensuring that extended diversion distance risks are mitigated.

Item [22]

The item amends subsection 7.05(5) to address the changes brought about by item [14] (about flight to an isolated destination aerodrome that is planned with a destination alternate aerodrome). Subsection 7.05(5) now makes clear that despite subsection 7.05(3) the fuel required by subsection 7.05(6) is only applicable when the diversion to a planned destination alternate aerodrome is not from a planned destination that is an isolated destination aerodrome.

Item [23]

This item clarifies the intended operation of paragraph 9.04(2A)(a).

Item [24]

This item amends subsection 9.04(2B) so that the definition of horizontal distance “D” supports this concept in subsection 9.04(5). Subsection 9.04(5) is inserted by item [26] and provides for the use of an alternative method of meeting the net take-off requirements.

Item [25]

This item amends paragraph 9.04(3)(b) to increase the maximum lateral obstacle assessment area half-width from 300 metres to 370 metres. This is necessary to ensure consistency with required navigation performance (RNP) accuracy and to maintain safety assurance.

Under the existing provision, operators using RNP 0.2 navigation specifications were permitted to apply a 300 metre lateral limit. However, this created a misalignment between the permitted obstacle assessment area and the actual containment capability of RNP 0.2, which corresponds to a lateral containment of approximately 370 metres. The discrepancy meant that aircraft could be dispatched with navigation accuracy requirements that could not be reliably maintained within the narrower 300 metre limit.

The amendment resolves this inconsistency by aligning the obstacle assessment area with the certified RNP capability, ensuring that aircraft operating under RNP 0.2 specifications maintain the required lateral containment during EODPs. This change supports safe operations by ensuring that obstacle clearance is based on achievable navigation accuracy.

Item [26]

This item repeals the current transitional provision that incorporated an alternative method of meeting net take-off flight path requirements set out in subsection 12A of CAO 20.7.1B. The amendment inserts new subsections (4A) to (5D). These provisions set out the alternative net take-off requirements that include the following elements:

(a) the obstacle assessment area (OAA) geometry requires a lateral commencement that is a minimum of either 90 metres from the runway centreline or half‑wingspan + 60 metres for aircraft with wingspan less than 60 m;

(b) the splay divergence rate is a minimum of 0.0625 × D (i.e. 6.25% of the distance from the departure point);

(c) half-width of the OAA must be the greater of:

 (i) 1 × RNP value certified for the aircraft in the one-engine-inoperative (OEI) condition; or

 (ii) 370 metres, regardless of whether the aircraft has better RNP capability (e.g. RNP 0.1 or 0.05).

The method includes the operational requirement that aircraft must not commence take-off if the actual navigation performance (ANP) exceeds the EODP design half-width RNP value (e.g. if the design is based on RNP 0.2, ANP must be less than or equal to 0.2 nm).

Subsection 9.04(4A) provides that subsection 9.04(5) applies only in relation to the flight of an aeroplane for which the requirements mentioned in section 9.04A are met. Section 9.04A (Competencies and design requirements—alternative RNP-based engine-out departure procedures) is inserted into the MOS by item [28].

Subsection 9.04(5) provides for subsection 9.04(2) the distances of the lateral commencement of the obstacle assessment area in relation to the wingspan of the aeroplane. It then prescribes the permitted splay divergence rate. It also includes the lateral limit of the obstacle assessment area mentioned in either subsection (5A) or (5B).

Subsection 9.04(5A) provides the maximum lateral distance of the obstacle assessment area from the aeroplane’s intended flight path can be limited to 370 m where the flight from the departure end of the runway to the lowest safe altitude for the route can be conducted with a navigation specification of RNP 0.2 or better.

Subsection 9.04(5B) provides the maximum lateral distance of the obstacle assessment area from the aeroplane’s intended flight path is limited to a maximum of the distance in nautical miles (converted to metres) of the navigation specification RNP value approved for the aeroplane where the flight from the departure end of the runway to the lowest safe altitude for the route cannot be conducted with a navigation specification of RNP 0.2 or better. A note is provided that makes clear that the reference to “RNP 0.2 or better” includes RNP capability that is more accurate than RNP 0.2, for example, RNP 0.15 which has a smaller RNP number value.

Subsection 9.04(5C) provides the meaning of approved for the aeroplane in relation to the navigation specification RNP value for use in subsection 9.04(5B).

Subsection 9.04(5D) inserts an operational requirement that the operator and the pilot in command must each ensure that immediately before commencing take-off, the portion of the flight from the departure end of the runway to the lowest safe altitude for the route can be conducted within the navigation specification used to determine the distance mentioned in paragraph (3)(b) or (4)(b), or subsection (5A) or (5B) which are intended to provide safety assurance between maintaining the intended flight path and associated obstacle assessment area.

Item [27]

This item repeals subsection 9.04(8) that provided a definition of CAO 20.7.1B, which is no longer used. The amendment is consequential to item [26] that repeals old subsection 9.04(5).

Item [28]

This item inserts new section 9.04A which provides the competencies and design requirements applicable in relation to the use of the alternative RNP-based engine-out departure procedures. Section 9.04A includes design requirements and design and approval conditions.

To use the alternative net take-off area requirements prescribed in subsection 9.04(4A) through to 9.04(5D), subsection (2) requires the operator of the aeroplane for the flight to be the holder of an approval to use a navigation specification of RNP AR DP for a flight of the aeroplane issued under regulation 91.045 CASR, for the purposes of subparagraph 91.660(1)(b)(i) of CASR, or if the aeroplane is a foreign-registered aircraft—by the national aviation authority of the aircraft’s State of registry or of the State of the operator.

Subsection (3) requires that the EODP must be designed by the holder of a procedure design certificate or authorisation issued under Part 173, or equivalent foreign authorisation issued by the FAA, EASA or national aviation authority of the United Kingdom, New Zealand or Canada. The authorisation does not authorise the procedure design, as Part 173 does not apply to engine-out procedure designs under subregulation 173.005(3). However, the requirement ensures the procedure is designed by a flight procedure design organisation with the capabilities required under Part 173.

These requirements are designed to ensure that obstacle clearance is maintained with high navigation accuracy and that the procedures are designed and implemented by qualified entities. The amendment aligns with international best practice and maintains an equivalent level of safety to the expiring transitional provisions.

Under subsection 9.04A(4), the EODP must provide for a flight track that is designed for use by aeroplanes using PBN-based course guidance. The subsection also requires that the design of the EODP flight track considers the ability of a pilot to initiate and maintain a desired speed and bank angle in a turn, the effect of wind on the take-off flight path, the effect of temperature on turns, and the effect of terrain proximity on TAWS warning.

Subsection 9.04A(5) prescribes that the aeroplane must be fitted with a TAWS-Class A (within the meaning of subsection 11.24(1)) that is operative for the flight.

Subsection 9.04A(6) prescribes that for subsection 9.04A(5) the operative TAWS-Class A requirement cannot be alleviated by section 11.25 (Flight with inoperative TAWS equipment).

Item [29]

The item inserts subsection 9.11(4) which provides that section 9.11 is subject to section 9.11A. See item [30].

Item [30]

The item inserts an alternative method for determining pre-flight landing distance requirements when the destination aerodrome is forecast to be wet or contaminated. It allows dispatch at higher landing weights than currently permitted, subject to additional safety controls.

Additional safety controls to support the measure are:

(a) a suitable destination alternate aerodrome must be planned that complies with unmodified MOS landing distance requirements; and

(b) the alternative method is not permitted where 2 destination alternates are required or for isolated destination aerodromes.

The amendment maintains the target level of safety by ensuring that a second safe landing option is available if the destination aerodrome becomes unsuitable due to runway surface conditions. It reflects international best practice and ICAO guidance (Doc 10064), which permits dispatch to a destination aerodrome with reduced landing performance margins when a fully compliant alternate aerodrome is planned.

Subsection 9.11A(1) prescribes the circumstances where the alleviation to destination aerodrome wet runway landing distance performance provided by subsection (2) can apply. They are where an authorised weather forecast indicates that the runway at the planned destination aerodrome, at the aeroplane’s estimated time of arrival, may be wet and where a destination alternate aerodrome is planned for a flight. It also precludes the use of the alleviation where the destination aerodrome is required to have 2 destination alternate aerodromes planned, such as to comply with section 4.10 requirements.

Subsection 9.11A(2) provides that despite the pre-flight landing performance requirements for wet runways prescribed in subsection 9.11(1), the operator and the pilot in command of the aeroplane for the flight must ensure that, when the flight begins, the landing distance available at the planned destination aerodrome is at least the landing distance required for a dry runway by subsection 9.10(1).

Subsection 9.11A(3) prescribes the circumstances where the alleviation to destination aerodrome contaminated runway landing distance performance provided by subsection (4) can apply. They are where an authorised weather forecast indicates that the runway at the planned destination aerodrome, at the aeroplane’s estimated time of arrival, may be contaminated and where a destination alternate aerodrome is planned for a flight. It also precludes the use of the alleviation where the destination aerodrome is required to have 2 destination alternate aerodromes planned, such as to comply with section 4.10 requirements.

Subsection 9.11A(4) provides that despite the pre-flight landing performance requirements for contaminated runways prescribed in subsection 9.11(3), the operator and the pilot in command of the aeroplane for the flight must ensure that, when the flight begins, the landing distance available at the planned destination aerodrome is at least the greater of 2 landing distance requirements. The first being not less than the landing distance required for a dry runway required by subsection 9.10(1). The second being not less than the distance required calculated in accordance with the performance data for the aeroplane under regulation 121.390 of CASR, where the data is specific to operations on contaminated runways.

Items [31] and [32]

The items amend subsection 11.24(1), paragraphs (a) of the definition of TAWS-Class A and TAWS-Class B to permit reference to the earlier technical standard order (TSO), namely, (E)TSO-C151a, in addition to the currently referenced (E)TSO-C151b and subsequent versions. TAWS is terrain awareness and warning system.

The amendments are intended to:

(a) recognise that (E)TSO-C151a and (E)TSO-C151b are based on the same underlying minimum operational performance standards (RTCA/DO-161A); and

(b) allow operators to use TAWS equipment certified to (E)TSO-C151a where it meets the required performance specifications; and

(c) enable continued use of aeroplanes fitted with TAWS equipment compliant with (E)TSO-C151a, which may otherwise be excluded under the current definition.

CASA has assessed that the safety control effectiveness of TAWS-Class A and Class B equipment is not diminished by referencing (E)TSO-C151a instead of (E)TSO-C151b.

Legislation Act 2003

Paragraph 10(1)(d) of the LA provides that an instrument will be a legislative instrument if it includes a provision that amends or repeals another legislative instrument. This instrument amends the Part 121 MOS that was registered as a legislative instrument and is, therefore, also a legislative instrument, subject to tabling and disallowance in the Parliament under sections 38 and 42 of the LA.

Sunsetting

Under paragraph 54(2)(b) of the LA, Part 4 of Chapter 3 of the LA (sunsetting of legislative provisions) does not apply in relation to a legislative instrument if the legislative instrument is prescribed by regulation for the purposes of the paragraph. The table in section 12 of the Legislation (Exemptions and Other Matters) Regulation 2015 sets out particular legislative instruments that are not subject to sunsetting for paragraph 54(2)(b). As far as is relevant, item 15 of the table specifies that an instrument relating to aviation safety made under CASR is not subject to sunsetting. Accordingly, the Part 121 MOS is not subject to sunsetting. This also applies to the MOS amendment.

The Part 121 MOS deals with aviation safety matters, which require a risk response or treatment plan. Accordingly, the Part 121 MOS is intended to have enduring operation, and it would not be appropriate for the Part 121 MOS to be subject to sunsetting. This also applies to the MOS amendment.

The exclusion from sunsetting affects parliamentary oversight by not requiring the Part 121 MOS to be remade and tabled before the end of the sunsetting period stated in Part 4 of Chapter 3 and, thereby, avoiding exposure to disallowance in the Parliament. In any event, any amendments of the MOS that are made, including the amendments in the current MOS amendment, are subject to tabling and disallowance in the Parliament. The MOS amendment will be repealed following the period during which it may be disallowed by a House of the Parliament, in accordance with section 48A of the LA.

Consultation

In accordance with section 17 of the LA, CASA undertook appropriate consultation prior to making this instrument amending the Part 121 MOS.

Consultation was conducted with the Part 121 ASAP TWG, comprising representatives from industry, operators and technical experts. CASA presented the proposed amendments to the TWG for review and discussion, including:

(a) removal of the requirement for category 4 RFFS at ERA within Australian territory for EDTO; and

(b) replacement of transitional EODP design criteria with contemporary RNP-based standards; and

(c) amendments to alternate aerodrome planning minima, isolated destination aerodrome provisions and landing performance requirements.

In addition to TWG engagement, CASA considered feedback received through exemption applications submitted by operators seeking relief from prescriptive requirements and operational variation approval assessments, which highlighted areas of operational constraint. CASA has also received direct industry correspondence.

CASA conducted public consultation on the proposed amendments via its Consultation Hub from 13 October to 10 November 2025. The consultation undertaken was appropriate and sufficient to satisfy the requirements of section 17 of the LA and Subpart 11.J of CASR. Industry comments were aligned with expectations and revealed no material new risks. CASA received feedback from 9 respondents associated with the 8 proposed changes affecting operational and technical standards for the Part 121 MOS amendments. Some respondents provided opposition only on the removal of the category 4 RFFS requirements in relation to ERA used for EDTO within Australia. CASA is satisfied that no further consultation is appropriate or reasonably practicable for this instrument for section 17 of the LA.

Sector risk, economic and cost impact

Subsection 9A(1) of the Act states that, in exercising its powers and performing its functions, CASA must regard the safety of air navigation as the most important consideration. Subsection 9A(3) of the Act states that, subject to subsection (1), in developing and promulgating aviation safety standards under paragraph 9(1)(c), CASA must:

(a) consider the economic and cost impact on individuals, businesses and the community of the standards; and

(b) take into account the differing risks associated with different industry sectors.

The cost impact of a standard refers to the direct cost (in the sense of price or expense) which a standard would cause individuals, businesses and the community to incur. The economic impact of a standard refers to the impact a standard would have on the production, distribution and use of wealth across the economy, at the level of the individual, relevant businesses in the aviation sector, and the community more broadly. The economic impact of a standard could also include the general financial impact of that standard on different industry sectors.

The proposed amendments to the Part 121 MOS have been assessed by CASA as maintaining an equivalent level of aviation safety while reducing regulatory burden and operational cost across the sector.

Impact on aviation sector risk

CASA conducted a comparative safety analysis using existing Australian rules, ICAO standards, and peer national aviation authority benchmarks. The amendments are designed to preserve the target level of safety by introducing alternative safety controls where prescriptive requirements are being alleviated. For example, removing the requirement for category 4 RFFS at EDTO ERA within Australian territory is assessed as not reducing safety, given the low likelihood of diversion and the absence of RFFS requirements at many departure and destination aerodromes. Similarly, replacing legacy EODP design criteria with contemporary RNP-based standards introduces new safety controls, including operator approvals and designer qualifications, ensuring continued safety assurance.

Impact on Economic Cost

The amendments are expected to reduce compliance costs for operators by:

(a) avoiding infrastructure requirements (e.g. RFFS at remote aerodromes); and

(b) enabling more efficient route planning and fuel uplift strategies; and

(c) allowing dispatch to wet or contaminated runways with adjusted landing performance margins; and

(d) supporting continued use of aircraft fitted with earlier standard TAWS equipment.

These changes will reduce fuel burn, emissions and operational overheads, particularly for operators serving regional and remote areas. CASA has considered the economic and cost impact on individuals, businesses and the community in accordance with subsection 9A(3) of the Act.

Impact on categories of operations

The proposed amendments to the Part 121 MOS are expected to have a positive and enabling impact across several categories of aircraft operation, particularly those subject to transitional provisions or operating under specific exemptions.

Part 121 operators conducting EDTO will benefit from the removal of the requirement for category 4 RFFS at ERA within Australian territory. This change removes a significant operational constraint and supports more flexible route planning. Operators approved to conduct EDTO will also benefit from the inclusion of RNP AR APCH as a valid IAP type for planning minima, allowing greater use of advanced navigation capabilities.

Part 135 operators using multi-engine aeroplanes who are required to comply with Part 121 performance rules will be affected by the proposed amendments to take-off and landing performance criteria. These changes modernise the EODP design requirements and introduce updated obstacle assessment parameters.

Part 121 operators to whom CASA EX74/24 – Part 121 – Single Pilot Aeroplane (MOPSC 10-13) Operations – Exemptions and Directions Instrument 2024 applies will be impacted by changes to TAWS definitions and landing performance rules. The amendments enable the use of TAWS equipment certified to (E)TSO-C151a, expanding the range of acceptable equipment and reducing compliance barriers.

Part 135 operators and operators to whom Subpart 121.Z applies (certain single-engine aeroplanes) will be affected by the revised definitions of TAWS-Class A and TAWS-Class B, which align with broader regulatory usage and support continued operation of aircraft fitted with earlier standard TAWS equipment.

There is also a general impact across the categories. The amendments provide increased operational flexibility, particularly in relation to planning for isolated destination aerodromes with alternate aerodromes, dispatching to wet or contaminated runways with adjusted landing performance margins, and using dual straight-in instrument approaches to reduce circling minima additives.

The changes are assessed as maintaining an equivalent level of safety while reducing regulatory burden and enabling more cost-effective operations. No adverse impacts are anticipated for any category of aircraft operation.

Impact on regional and remote communities

The proposed amendments to the Part 121 MOS are expected to have a positive impact on regional and remote communities by improving the accessibility and reliability of air services to isolated destinations. Specifically, the amendments permitting operators to plan flights to isolated destination aerodromes with a destination alternate aerodrome–subject to enhanced fuel planning–will enable operations in weather conditions that would otherwise prohibit dispatch. This change is particularly relevant to communities served by aerodromes such as Lord Howe Island, where the absence of a nearby alternate aerodrome has historically limited service availability.

The increased likelihood of service to these locations is expected to have a positive outcome on public and social interests, supporting community connectivity, economic activity and access to essential services. The amendments do not impose additional costs on operators but provide operational flexibility, allowing them to choose between the existing prescriptive requirements or the new alleviated provisions.

Operators choosing to benefit from the amendments in relation to isolated destination aerodromes will be required to update their operational documentation and manage changes through their internal change management processes.

Overall, the proposed changes support CASA’s objective of maintaining aviation safety while enabling more practical and sustainable operations to remote and regional areas.

Office of Impact Analysis

An Impact Analysis (IA) was prepared by CASA for the new Part 121 of CASR (in the form of the then utilised Regulatory Impact Statement or RIS).

The RIS was assessed by the Office of Best Practice Regulation (OBPR) as compliant with the Best Practice Regulation requirements and contained a level of analysis commensurate with the likely impacts (OBPR id: 24505).

An IA is not required in this case, as the instrument is covered by a standing agreement between CASA and OIA under which and IA is not required for amendments to Manuals of Standards (OIA reference number: OIA23-06250).

Statement of Compatibility with Human Rights

The Statement of Compatibility with Human Rights at Attachment 1 has been prepared in accordance with Part 3 of the Human Rights (Parliamentary Scrutiny) Act 2011.

Making and commencement

The instrument has been made by the Director of Aviation Safety, on behalf of CASA, in accordance with subsection 73(2) of the Act.

The instrument commences at the time that it is registered and is automatically repealed in accordance with section 48A of the LA.

Attachment 1

Statement of Compatibility with Human Rights

Prepared in accordance with Part 3 of the
Human Rights (Parliamentary Scrutiny) Act 2011

Part 121 (Australian Air Transport Operations—Larger Aeroplanes)
Amendment Manual of Standards 2025

This legislative instrument is compatible with the human rights and freedoms
recognised or declared in the international instruments listed in section 3 of the
Human Rights (Parliamentary Scrutiny) Act 2011.

Overview of the legislative instrument

Purpose

The instrument amends the Part 121 (Australian Air Transport Operations—Larger Aeroplanes) Manual of Standards 2020 (the Part 121 MOS).

The Part 121 MOS sets out the standards for the operational, procedural and safety risk management standards for the conduct of Australian air transport operations in larger aeroplanes. The MOS consolidates the existing rules of the air and contains some new rules to enhance operational flexibility, improve aviation safety and bring Australian requirements more in line with the Standards and Recommended Practices of the International Civil Aviation Organization.

The instrument includes amendments that address transitional provisions in the Part 121 MOS introduced at commencement in December 2021 to support industry transition from legacy Civil Aviation Orders and the Civil Aviation Regulations 1988, that previously contained the flight operations rules, to the new flight operations regulations (comprising Parts 119, 121, 133 and 135 of the Civil Aviation Safety Regulations 1998 (CASR)). Transitional arrangements included a requirement (due to have commenced on 2 December 2025) for category 4 rescue and firefighting services capability to apply for en-route alternate aerodromes used for extended diversion time operations (EDTO). The instrument repeals the proposed requirement, to avoid unintended consequences relating to the proposed standard at paragraph 4.19(2)(d) of the Part 121 MOS, such as limiting EDTO or requiring costly infrastructure upgrades at remote aerodromes. This alleviation reflects infrastructure limitations and the very low likelihood of diversion to these aerodromes. Operators will continue to comply with other EDTO safety requirements.

The instrument provides an enduring alternative method to comply with performance rules regarding engine-out departure procedures, to replace the alternative method set out in subsection 12A of Civil Aviation Order 20.7.1B, that had been incorporated into the Part 121 MOS (the incorporation of which expires at the end of 1 December 2025). Broadly, the changes are expected to improve operational efficiency by enabling higher dispatch weights, reduced fuel burn, and lower emissions. This will enable operational flexibility while preserving safety through alternative controls (e.g. requiring operator approvals and the use of accredited procedure designers). It is expected that the amendments would encourage adoption of advanced navigation capabilities (e.g. required navigation performance authorisation required (RNP AR DP)) and modern safety systems (e.g. TAWS-Class A, being a type of terrain awareness and warning system), enhancing long-term safety performance.

The instrument amends a number of prescriptive requirements relating to alternate aerodrome planning minima, landing performance on wet or contaminated runways and isolated destination aerodrome planning. There are some alleviations to the landing performance requirements for wet or contaminated runways. Operators may now dispatch aeroplanes to destination aerodromes forecast to be wet or contaminated at higher weights, provided a compliant destination alternate aerodrome is planned. This change introduces operational flexibility while maintaining safety with the use of additional planning controls.

The instrument provides for alternate aerodrome minima to be no more restrictive than destination minima and permit isolated destination aerodromes to be planned with an alternate aerodrome under enhanced fuel requirements. The changes regarding destination isolation aerodromes are expected to support regional and remote connectivity, by permitting flights to isolated aerodromes under specified conditions, and reducing the likelihood of service cancellations.

Other minor or technical amendments align definitions of instrument approach procedures with changes recently made to the Part 91 Manual of Standards, and otherwise correct editorial errors or clarify the intention of provisions.

Overall, the amendments represent a continuation of existing policy settings with targeted refinements to align with contemporary operational practices and international standards.

CASA has assessed the impact of these amendments on aviation safety in accordance with section 9A of the Civil Aviation Act 1988 (the Act). The proposed changes maintain an equivalent level of safety to existing provisions by introducing alternative safety controls where prescriptive requirements are alleviated. These controls include operator approvals, accredited procedure designers and enhanced planning requirements. CASA considers the amendments necessary and appropriate to ensure safe, efficient and cost-effective operations while supporting continued service to regional and remote communities.

Human rights implications

The instrument may engage the following human rights:

• the right to life under Article 6 of the International Covenant on Civil and Political Rights (the ICCPR)
• the right to work under Article 6(1) and the right to safe and healthy working conditions under Article 7 of the International Covenant on Economic, Social and Cultural Rights (the ICESCR).

Right to life under the ICCPR

Right to safe and healthy working conditions under the ICESCR

The instrument may engage these rights. This engagement is in the context of CASA’s statutory purpose. The aim of CASA and its regulatory framework, including Part 121 of CASR and its related MOS, is to uphold aviation safety by prescribing the conduct of individuals and organisations involved in large aeroplane air transport operations. It is, therefore, a threshold requirement for all CASA legislative instruments that they preserve, promote and enhance aviation safety. Insofar as the Part 121 MOS is crafted and intended, as far as practicable, to promote and enhance aviation safety standards for flight operations it promotes the right to life under Article 6 of the ICCPR by legislating for safer conditions that will minimise the risk of accidents and prevent accidental death. Thus, for Article 7 of the ICESCR, the Part 121 MOS also promotes the right to safe and healthy working conditions for all pilots and crew of larger aeroplanes.

Right to work

The instrument may engage the right to work that is protected under Article 6(1) of the ICESCR. This right includes the right of everyone to the opportunity to gain their living by work which they freely choose or accept.

The instrument does not directly address the right to work. However, the provisions may have an impact on the way that the work involved in safely operating an aircraft is carried out. Many obligations of care, skill, technique and procedure are imposed on pilots to this end. Failure to follow the relevant requirements of the Part 121 MOS when flying an aircraft could result in the loss of a licence or the loss of continued employment. However, in the interests of aviation safety, it is necessary that pilots follow the flying rules.

The amendments primarily enhance aviation safety and operational clarity. They do not impose arbitrary restrictions on rights. Any incidental impact on work or movement is proportionate and consistent with the objectives of the Act and Australia’s human rights obligations. Accordingly, any potential limitation on the right to work is itself necessary, reasonable and proportionate in achieving the aim of protecting and improving aviation safety consistent with the objects of the Act and the regulations.

Conclusion

The instrument is compatible with human rights and, to the extent that it may also limit human rights, those limitations are reasonable, necessary and proportionate to ensure the safety and integrity of the aviation safety system on which all aviation operations rely.

Civil Aviation Safety Authority