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UK Civil Aviation Regulations

These are published by the CAA on our UK Regulations pages. EU Regulations and EASA Access Guides published by EASA no longer apply in the UK. Our website and publications are being reviewed to update all references. Any references to EU law and EASA Access guides should be disregarded and where applicable the equivalent UK versions referred to instead.

Part 145 Maintenance Organisation Approval holders provide maintenance services in accordance with Regulation (EU) No 1321/2014 as retained (and amended in UK domestic law) under the European Union (Withdrawal) Act 2018

This page includes details and links to regulation, policy and guidance. It will provide approval holders resources to ensure they remain compliant with not only the regulations but also UK Civil Aviation Authority (CAA) policy.

Guidance material provides interpretation or amplify in greater detail certain areas or aspects of regulation and/or policy to allow an approval holder to fully implement quality systems which remain compliant and perform well.

Alerts and notifications

Tailored news, notifications and alerts from the CAA, including alerts issue in the last 12 months are available through SkyWise.


Maintenance Organisation Exposition (MOE) should be constructed using the Part 145 MOE Guidance (CAP 2375) and associated MOA Checklist

Part 145 Occasional and Temporary Line Stations sets out what the CAA considers as a Part 145 occasional or temporary line station, how they may be established and the periods of time that they may remain in place.

Acceptance of maintenance tasks carried out by pilots; Part 145 caters for certain maintenance tasks to be carried out by the aircraft commander at an unsupported location. AMC to Part 145.A.30(j)4 lists a number of maintenance tasks which a qualified pilot may be issued an Authorisation to carry out. Other checks or replacements involving simple techniques which are not listed in Part 145 AMC 145.A.30(j)4 require specific agreement from the CAA.

Part 145 Maintenance Staff Employment Status, the Information Notice provides guidance to enable Part-145 organisations to establish the employment status of staff engaged on zero hours contracts and those engaged indirectly for the purposes of Part 145.A30(d).

Part 145 Applicability of AMC2 145.A.50(d) and Certification of Used Aircraft Components clarifies the use of AMC2 145.A.50(d) so that the CAA, installers and operators have confidence that used aircraft components have been satisfactorily removed from the aircraft, inspected, assessed and tested, as necessary, before being certified and made eligible for installation on an aircraft registered in the UK.

There have been various interpretations of the requirements which at times have led to organisations not being fully prepared or capable of providing the scope of work that they have applied for or have been approved to provide.

The purpose of this policy note is to remove ambiguity about what the UK CAA expects of an organisation applying for Part 145 approval or wishing to continue to hold Part 145 approval.

Part 145 Loss of Capability

UK Regulation (EU) No. 1321/2014, Part 145.A.85 requires the organisation to notify the Civil Aviation Authority (CAA) of any proposal to make changes to the organisation. This also includes changes to the facilities, equipment, tools, material, procedures, work scope, certifying staff and airworthiness review staff that could affect the approval.

Part 145.A.80 and its Acceptable Means of Compliance (AMC) provides for the situation where an organisation may temporarily not hold all the necessary tools, equipment and so on, for an aircraft type or variant specified in its exposition and/or approval certificate. The regulation provides a means for the CAA to defer revoking the lost capability when it considers the loss to be temporary, and where there is a demonstrable commitment from the organisation to re-establish full capability before maintenance recommences.

Actions to be taken where Capability to perform the full scope of work is temporarily lost

The CAA have decided that it will not immediately revoke an aircraft type or rating from an organisation’s approval certificate when the capability to maintain a particular product, part or appliance is considered to be temporarily lost. This is based on the organisation agreeing to amend their Maintenance Organisation Exposition (MOE) to reflect the change of capability and to have procedures in place to re-establish compliance with Part 145 before reinstating the particular capability. This policy is not applicable when the CAA considers that an organisation is generally failing to meet its regulatory obligations and that it would be more appropriate to suspend, limit or revoke the approval.

An organisation that temporarily does not have the ability to fulfil the Part 145 requirements, (such as the loss of personnel within an organisation and so on), the CAA will allow six months for the organisation to re-establish full compliance before suspension/revocation of the capability in question is considered. (This corresponds to the normal maximum permitted duration of a level 2 finding).

If the organisation has not re-established the capability after six months, they will be informed in writing that the affected type/rating should be greyed out in the scope of work section of the MOE, signifying that the organisation has temporarily lost the identified capability, and consequently is unable to exercise the privileges of the approval granted in accordance with Part 145.A.75. Unless the organisation can demonstrate a commitment to re-instate the capability, the affected capability will be revoked and the approval certificate amended accordingly.

Please note that demonstration of commitment must be presented; acceptable examples are purchase orders, invoices, Letters of Intent, contracts, press/publication adverts.

To re-instate greyed out capability the organisation will need to demonstrate compliance with all applicable paragraphs of Part 145, before an amendment to the MOE can be approved reinstating the approval privileges.

Where an organisation has not re-established a capability greyed out in accordance with this Policy at the time when the continuation recommendation is required, unless the organisation can demonstrate full compliance, the CAA will consider that the capability is lost and that it will be unable to make a continuation recommendation. The specific product, part, appliance, or process will be revoked and removed from the organisation’s approval certificate. The greying out of a capability will not be allowed to continue past the point at which a continuation recommendation in accordance with Part 145.B.30 is required.

Organisations who do not follow the process, will be subject to normal procedures for the resolution of findings and may have an aircraft type or rating revoked immediately when the capability to maintain a particular product, part or appliance is lost.

Close Part 145 Loss of Capability

Facilities (145.A.25)

Any Part 145 organisation must have facilities commensurate with the scope of work for which it is approved to provide.

Line Maintenance providers are expected to have an office, storage facilities and, for larger providers, possibly a workshop. These facilities must be airside or at the very least within a short drive. The distance should be reasonable and appropriate for the activity being provided from the airside area. This is to ensure personnel from the organisation are not operating remotely from the approved facility.

Base maintenance providers must have a hangar which accommodates the aircraft types for which they are approved to maintain with offices, storage facilities and workshops as required. The aircraft type must be able to be completely enclosed by the facility. It is not acceptable for the aircraft tail to be outside the hangar while performing base maintenance. Work may be performed outside the hangar subject to procedures being approved in the Organisations Maintenance Organisation Exposition (MOE).


Close Facilities (145.A.25)

Maintenance Data (145.A.45)

Generic Maintenance data for each aircraft type within the requested or approved scope of work must be available at the organisation at all times. This data should be used in the initial approval stages to define tooling requirements and assist in the creation of the manpower plan. It will define manpower requirements for each task. It will also need to be available during subsequent Civil Aviation Authority (CAA) audits. This helps to demonstrate the organisation's overall capability to perform maintenance.

The data does not have to be up to date at all times (although it needs to be controlled) and may be supplemented with customer supplied data specific to a particular model/fleet. Where customer supplied data is not used, a subscription service will need to be in place prior to commencement of any work. The organisation must have procedures in place that demonstrate how they control the data and ensure that it is up to date before use.

It is not acceptable for data to be supplied solely by the customer directly prior to an aircraft input. This will not allow appropriate production planning to take place prior to any work being performed.


Close Maintenance Data (145.A.45)

Tooling and Equipment (145.A.40)

Organisations must have all tooling which is required to complete the maintenance tasks within their scope of work permanently available at their facilities. The exception to this requirement is where a task is only performed infrequently (as a guide, tasks that are performed at one in three of similar inputs) then the tooling can be acquired at the time the task is performed (through loan or pool arrangements).

The appropriate tooling for the scope of work may be supplied through a contract with an organisation that supplies, maintains and updates/replaces the tooling held by the Part 145 organisation is acceptable. The tooling should be provided on a permanent basis and its availability should not be dependent on a contract with an operator. It remains the responsibility of the Part 145 organisation to determine that the tooling is of the correct type and is in a condition that is suitable for use.

Each organisation must ensure it has sufficient staging and access equipment to gain access to all areas of the aircraft that fall within the approved scope of work. Access equipment or staging should be of a suitable type to allow the maintenance task to be performed in an effective manner. Staging and access equipment should provide a stable working area where tools and materials can be located while performing the task to ensure that potential Human Factors issues are minimised.

All tooling and equipment must be controlled through a register and maintained or calibrated to Original Equipment Manufacturer (OEM) requirements/national standards. This includes servicing of Aircraft Jacks, Staging and Access Equipment.

Alternative or locally fabricated tools may only be used when there is an approved procedure in the Maintenance Organisation Exposition (MOE) that ensures an assessment of the suitability of alternative tooling has been carried out, and that the use of the alternative tool has been properly validated. This is to ensure any such tools are of an equivalent specification, standard and accuracy as those specified in the applicable maintenance data provided by the OEM.

Close Tooling and Equipment (145.A.40)

Certifying staff and Manpower Resources (145.A.30, 145.A.35)

The organisation shall have sufficient staff to plan, perform, supervise, inspect and quality monitor the activities which the organisation is approved to perform. This must be supported with a manpower plan which shows either Planned vs Actual man-hours for work which is scheduled and has been completed at the organisation or provides a capacity projection based on number of staff available and envisaged scope of work, including the assumptions made to develop the plan (such as number of staff needed to complete a check or number of persons to run a roster at a line station, typical level of defects and scheduled maintenance workload for a night stopping aircraft). This can then be used to establish the maximum capacity and scope of work the organisation can undertake.

The plan must take into consideration the following:

Training, leave and an allowance for sickness and so on.

An efficiency level should be declared by the organisation. It is not feasible to be 100% efficient. Human performance principles suggest that a figure of 80% or less is more realistic when taking account of human factors.

Resilience within the organisation: it is not possible to hold an approval based on one person's licence for aircraft where an A1 rating is required. The GM to 145.A.10 explains the limitations and permissible arrangements for organisations maintaining non-complex aircraft.

Part 145.A.30(h) requires an organisation to have appropriate aircraft type rated certifying staff qualified in category C in accordance with Part-66, supported by sufficient aircraft type rated staff qualified as category B1 and B2 in accordance with Part-66. Organisations must be able to demonstrate their ability to maintain compliance, even when some staff are not available. This will ensure an aircraft's maintenance is not compromised or halted due to sickness or other non-availability of some staff.

Close Certifying staff and Manpower Resources (145.A.30, 145.A.35)

Authorisations issued under UK Part 145.A.30(j) and Appendix IV

Appendix IV to UK Regulation (EU) No 1321/2014, Annex II (UK Part 145) prescribes the conditions under which authorisations may be issued by UK CAA approved Part 145 organisations that are based outside the UK, or UK based organisations that have some facilities outside the UK, to certifying staff not qualified in accordance with UK Part 66.

To prevent any misunderstanding of this requirement, our  policy is outlined below. 

A maintenance organisation using UK Part 145 Appendix IV certifying staff, who do not hold an appropriate UK Part 66 Aircraft Maintenance Licence, is required to comply with UK Part 145 Appendix IV in full, even if they have the aircraft type endorsed on the licence issued by their National Aviation Authority.

Where appendix IV to UK Part 145 refers to certifying staff and base maintenance support staff, they need to demonstrate that they have received type training and passed examinations at the category B1, B2 or B3 level, as applicable and referred to in Appendix III to UK Regulation (EU) No 1321/2014, Annex III (UK Part 66) for each aircraft type. This means a type training course carried out in accordance with UK Part 66 by a UK CAA approved Part 147 Maintenance Training Organisation. 

The UK, through various exemptions that were applicable up to and including 31 December 2022, has accepted EASA approved Part 147 type training courses as being equivalent to UK Part 147 training courses.  With effect from 1 January 2023, certifying staff authorisations, issued by organisations approved in accordance with UK Part 145 that are based outside the UK, or are UK based and have some facilities located outside the UK, require type training courses to be carried out by a UK Part 147 approved organisation, or have the type training course directly approved by us.

Certificates of Recognition (CofR) for type training courses completed and dated before 1 January 2023 remain acceptable.

Exceptions may apply where there is a bilateral agreement or working arrangement in place.  

Examples where there is no bilateral agreement or working arrangement in place between the UK and the State of the licence holder are;

An EASA Part 66 AML issued on 21 December 2022 with B1 / B2 A350-900 endorsement. Valid for UK Part 145 authorisation.

An individual working for a maintenance organisation in a state outside the EU who holds a national licence of that state which is in compliance with ICAO Annex 1 and holds a CofR for an EASA Part 147 approved type training course completed on 10 June 2022 for a Boeing 777-300. Valid for UK Part 145 authorisation.

An individual holding an EASA Part 66 AML, or national licence issued which is in compliance with ICAO Annex 1, who has completed an EASA Part 147 type training course with a CofR, issued on 3 January 2023. Not valid for UK Part 145 authorisation.


Close Authorisations issued under UK Part 145.A.30(j) and Appendix IV

Maintenance Organisation Exposition (145.A.70)

The Maintenance Organisation Exposition (MOE) is integral to an organisation's ability to demonstrate its capability and compliance with Part 145. Statements that are open or ambiguous create the potential for misunderstanding, non-compliance with the regulation and could result in regulatory action, aircraft grounding or worse. The MOE must be fully reviewed on a regular basis by the organisation and by the Civil Aviation Authority (CAA) during the audit cycle. The procedures contained in an exposition should describe the detailed process that the organisation follows to comply with the applicable provision in the regulation. They should not simply be policy statements indicating that the organisation will comply with the relevant elements of the regulation when using a process/procedure.

The exposition should keep up to date and follow the guidance set out in the Part 145 MOE Guidance (CAP 2375) and associated MOA Checklist.

Close Maintenance Organisation Exposition (145.A.70)

Line Maintenance

Line Maintenance generally refers to minor, unscheduled or scheduled maintenance carried out on aircraft that includes:

  • Unscheduled maintenance resulting from unforeseen events (for example, trouble shooting, defect rectification).
  • Scheduled tasks not exceeding the weekly check or equivalent specified in the approved aircraft maintenance programme.
  • Scheduled checks that contain servicing and/or inspections that do not require specialised training, equipment, or facilities, and that have been assessed and accepted for inclusion in the line maintenance scope of work.
  • Component replacement with use of external test equipment if required. Component replacement may include components such as engines and propellers, where environmental conditions are suitable.
  • Maintenance performed on aircraft after a period of being out of service (such as aircraft in storage) when agreed in advance with the Civil Aviation Authority (CAA).
  • The need to access a hangar (even if the activity is permitted under a line maintenance scope of approval) considering the type of aircraft, the maintenance event type/complexity, the environmental and weather conditions.

It is not Line Maintenance when:

There are a significant number of different types of tasks to be carried out during a single input, even if when considered singularly they may still fall within the definition of line maintenance but together clearly require the use of base maintenance production planning support and/or base maintenance release to service process (category C staff supported by B1/B2 support staff) in order to ensure that the maintenance ordered has been properly carried out before release to service.

Replacement of any major component where the related maintenance procedures clearly require the use of a hangar environment requiring special ground support equipment and/or structured production planning and/or complex and lengthy maintenance.

Any scheduled maintenance task which requires extensive disassembly of the aircraft and/or extensive in-depth inspection.

Close Line Maintenance

Major repairs and/or major modifications

Trouble shooting and/or Defect Rectification requiring special ground support usually relevant to base maintenance (for example, special equipment, structured production planning, complex and lengthy maintenance).

A scheduled maintenance event, which in the planning phase has been already identified as significant in terms of duration and/or man-hours.

A work package requiring a complex team composition in terms of numbers and categories (avionic, structure, cabin, NDT and so on.) of staff involved per shift.

The management of the event by B1 and B2 support staff and the release by a C certifying staff.

Close Major repairs and/or major modifications