How to apply for a UK CAA Part-66 aircraft maintenance licence

Becoming a licensed aircraft maintenance engineer is one thing. Demonstrating to the regulator that you are qualified to certify aircraft maintenance is another.

A UK Civil Aviation Authority (CAA) Part-66 Aircraft Maintenance Licence (AML) confirms that you have the required knowledge and practical experience and, where applicable, aircraft type training. It allows you to exercise maintenance privileges within the categories and ratings shown on the licence.

This guide explains how to apply for a UK CAA Part-66 licence, what evidence you need, how the process works and where applicants commonly lose time.

What is a UK CAA Part-66 licence?

A UK Part-66 AML allows suitably qualified engineers to certify maintenance on aircraft within the categories and ratings listed on their licence.

The principal licence categories are:

• Category A, line maintenance certification for specified tasks
• Category B1, mechanical maintenance, including airframe, engine and mechanical or electrical systems
• Category B2, avionics maintenance
• Category B2L, limited avionics maintenance covering specified system ratings
• Category B3, piston-engine, non-pressurised aeroplanes
• Category C, base maintenance certification

The category you apply for determines the knowledge examinations, practical experience and supporting evidence required. Before relying on a particular training or licensing route, compare the current UK requirements with the official Part-66 requirements published by EASA, where relevant to your circumstances.

A licence does not, by itself, authorise you to certify every aircraft you encounter. Aircraft type ratings, organisational authorisation and the scope of your employment also apply. The licence is the foundation of your certification privileges, not a general authorisation to certify any aircraft.

Before you apply, choose the right category

Start by identifying the licence category or sub-category that matches your intended work.

• A B1.1 licence relates to turbine-engine aeroplanes.
• A B1.2 licence relates to piston-engine aeroplanes.
• A B2 licence covers avionics.
• A B2L licence is limited to particular avionics system ratings.
• A Category C licence is generally associated with base maintenance certification and has its own experience routes.

You should also establish whether you are applying for:

• An initial Part-66 licence
• An additional category or sub-category
• An aircraft type rating
• Renewal of an existing licence
• Removal or amendment of a limitation

The CAA may require different evidence depending on the service you need.

Meet the knowledge requirements

Applicants generally demonstrate the required theoretical knowledge by passing the relevant Part-66 module examinations.

These modules cover subjects such as:

• Mathematics
• Physics
• Electrical fundamentals
• Electronic fundamentals
• Digital techniques
• Materials and hardware
• Maintenance practices
• Basic aerodynamics
• Human factors
• Aviation legislation
• Aircraft systems
• Propulsion
• Gas turbine and piston engines, where applicable

The exact modules depend on your category. Approved training organisations can help you plan the required examinations and may offer classroom, online or blended training. You can also use our Part 147 training schools directory to compare approved training options.

A relevant technical qualification or approved training course may provide credits or exemptions in certain circumstances. Do not assume that a general engineering qualification automatically satisfies the Part-66 knowledge requirements. The CAA will assess the evidence against the applicable rules.

The CAA may ask an applicant for original documents supporting an application for the initial issue, renewal or amendment of a UK Part-66 licence. Keep certificates, examination records, training documents and identity evidence organised and available.

Build the required practical experience

Passing examinations is only one part of the application. You must also demonstrate practical maintenance experience relevant to the category and privileges requested.

Your experience should show genuine involvement in aircraft maintenance, rather than simply time spent working near aircraft. Typical evidence may include:

• An experience log or task record
• Employer statements
• Details of the aircraft types and systems on which you worked
• Dates and duration of employment
• Maintenance organisation approval details
• Descriptions of the tasks performed
• Supervisor or certifying staff signatures
• Evidence that the work covered the relevant category or sub-category

The CAA will assess whether the experience is recent, relevant, properly documented and gained in an appropriate maintenance environment.

Before submitting your evidence, review our guidance on common CAP 741 logbook mistakes that can delay a licence application.

Category B2 experience

Applicants for avionics licences should demonstrate experience involving aircraft systems that transfer, process, display or store analogue or digital data.

Relevant work may include:

• Line-replaceable units (LRUs)
• Interfaces and connectors
• Data lines and data buses
• Coaxial cables
• Wireless data transmission systems
• Wiring installation and protection
• Avionic displays
• Communication, navigation and surveillance systems
• Aircraft data-processing equipment

Describing yourself as an avionics engineer is not sufficient on its own. The evidence should show what you maintained and how the work relates to the requested privileges.

Category B2L experience

Applicants for Category B2L must demonstrate one of the applicable experience routes. Where the applicant has no previous relevant technical training, one route requires three years of practical maintenance experience on operating aircraft, covering the corresponding system rating or ratings.

Because B2L is limited to specified system ratings, the experience must correspond to the systems requested. A broad collection of unrelated technical tasks may not establish eligibility.

Consider an approved training route

There are several ways to build the knowledge and experience required for a Part-66 licence.

Self-study and examinations

You can study the required modules independently and sit examinations through an approved examination or training organisation. This route is flexible, but it places greater responsibility on you to plan the correct modules and maintain suitable experience records.

Part-147 basic training

A Part-147 approved organisation may provide an approved basic training course. Depending on the course and qualification, this may reduce the practical experience required or provide examination credits.

Employer-based development

Many engineers build their experience through employment with an approved maintenance organisation. This route combines supervised practical work with exposure to established maintenance procedures and records.

Check the details before committing to any route. A training course is not automatically a complete licence application package.

Add an aircraft type rating

A basic licence category does not necessarily include a particular aircraft type. To exercise privileges on a specific aircraft, you may need to add an aircraft type rating. For a detailed overview, read our guide to adding a type rating to a Part-66 licence.

The usual process includes:

1. Completing the required aircraft type training
2. Passing the applicable examination or assessment
3. Completing on-the-job training (OJT), where required
4. Obtaining evidence from an appropriately approved organisation
5. Applying to the CAA to add the type rating

The CAA fee for adding a type rating is currently £183.00 per type rating. Check the current fee before applying.

OJT requirements

Where OJT is required, it must be carefully planned. Under Appendix III to Part-66, OJT must be started and completed within three years of the date of application.

AMC to Appendix III, Part-66, Section 6 requires that no more than 50 per cent of the OJT is completed before the theory training. OJT that does not meet these requirements may be rejected.

The maintenance organisation's exposition should include an OJT procedure. At a minimum, that procedure should explain:

• How the OJT programme is structured
• Which tasks must be completed
• How tasks are supervised
• Who is authorised to sign task records
• How competence is assessed
• How records are controlled and retained
• How the organisation confirms that the work meets Part-66 requirements

If you plan to complete OJT outside the UK, contact the organisation before starting. The CAA recommends verifying the validity of the organisation's UK OJT approval in advance. Our guide to EASA OJT approval for UK Part-145 organisations provides additional context.

Create a CAA Customer Portal account

Applications for a UK Part-66 licence are submitted online through the CAA Customer Portal.

If you have not used the portal before, create an account before accessing the online application form.

Once registered, start the application by selecting Aircraft maintenance licence applications from the available services.

Allow time to create and verify your account before you intend to submit the application. Portal access, identity details and supporting documentation should be ready before you begin the form.

Gather your documents

The application requires evidence supporting the licence or rating requested. Depending on your circumstances, this may include:

• Proof of identity
• Your existing UK Part-66 licence, if applying for an extension or amendment
• Examination certificates
• Training certificates
• Evidence of approved basic training
• Employment records
• Maintenance experience summaries
• Logbooks or task records
• Employer or maintenance organisation statements
• Aircraft type training certificates
• OJT records and completion statements
• Evidence of relevant technical qualifications
• Documents supporting any claimed credit or exemption

For an application to extend an existing licence, you must hold a UK Part-66 AML and meet the relevant knowledge and experience requirements for the additional category or sub-category.

Make sure names, dates, signatures, organisation details and licence numbers are consistent across your documents. Small inconsistencies can lead to requests for clarification and delay an otherwise complete application.

Submit the online application

Once you have met the requirements, complete the Aircraft Maintenance Licence online application form on the CAA Portal.

The CAA provides an AMEL portal form user guide to support applicants through the process. Use it, particularly if you are applying for more than one category, sub-category or service.

When completing the form:

• Select the correct application type
• Identify each category, sub-category or rating requested
• Upload clear and complete evidence
• Check that experience records cover the relevant privileges
• Include explanations where the evidence is not self-explanatory
• Review the application before submitting it
• Pay the applicable fee

The CAA may request original documents after submission. Retain the originals and do not dispose of them after uploading digital copies.

Understand the application fees

The CAA fee for an initial Part-66 licence application is currently £455.00 per category or sub-category applied for.

If you apply for additional services, the relevant fee also applies. Adding an aircraft type rating currently costs £183.00 per type rating.

Check the fee shown by the CAA when applying, particularly if you are submitting several requests together. Fees can change, and an application involving multiple categories or services may cost more than the headline figure.

How long does the application take?

The CAA's service-level agreement for initial Part-66 licences is 31 working days. This comprises:

• 10 working days for the initial assessment by a Licensing Officer
• 20 working days for the Surveyor's technical assessment of on-the-job experience
• One additional day for issuing and dispatching the licence

This timeframe assumes that the application and supporting evidence are complete and suitable for assessment. If the CAA needs further information, the process may take longer.

The best way to protect the timeline is to submit a complete, internally consistent application at the first attempt.

What happens if the CAA asks for more information?

A request for further information is not necessarily a rejection. It usually means that the assessor needs clarification or stronger evidence.

Respond promptly and provide exactly what has been requested. Common reasons for follow-up include:

• Missing signatures
• Unclear employment dates
• Insufficient detail in task records
• Experience that does not clearly match the requested category
• Unverified training documents
• Incorrect or incomplete OJT evidence
• Conflicting information between forms and supporting records

Avoid sending a large, unsorted collection of documents. A clear response that maps each document to the CAA's question is easier to assess.

Keep the licence valid

A Part-66 licence has an expiry date and ceases to be valid on that date in accordance with 66.A.40, Continued validity of the aircraft maintenance licence.

Until the CAA has renewed the licence in accordance with 66.B.120, Procedure for the renewal of an aircraft maintenance licence validity, and the licence has been signed by the licence holder, the privileges of an expired licence must not be used.

Do not continue certifying maintenance on an expired licence while renewal paperwork is in progress.

Monitor the expiry date well in advance and apply for renewal with sufficient time for the CAA to process the request. Once renewed, check the licence details carefully and sign it as required.

Practical application checklist

• Created a CAA Customer Portal account
• Selected the correct application service
• Chosen the correct category, sub-category or rating
• Passed the required examinations
• Completed the required practical experience
• Prepared relevant and signed experience records
• Confirmed any applicable training credits
• Completed compliant OJT, where required
• Verified the approval status of any OJT organisation
• Uploaded clear supporting documents
• Retained the original documents
• Paid the correct fee
• Checked the application for inconsistent dates or details
• Allowed for the CAA's assessment timeframe

Final considerations

Applying for a UK CAA Part-66 licence is an evidence-based assessment of your technical knowledge, practical experience and readiness to take responsibility for aircraft maintenance.

Identify the requirements, gather the correct evidence, record everything clearly and check the completed application before submission. A well-prepared application is easier for the CAA to assess and less likely to require corrective action.

For help reviewing your maintenance records before you apply, analyse your Part-66 logbook today.