Aircraft Maintenance Licence

What is the AML?

The Aircraft Maintenance Licence (AML) is the credential that grants an engineer the legal authority to certify that maintenance work on a commercial aircraft has been carried out to the required standard. It is issued under EASA Part-66 by the national aviation authority of the engineer's country of residence — in Latvia, by the Civil Aviation Agency — and it is the document that transforms a trained technician into an independently authorised certifying engineer.

The AML is not simply a qualification certificate. It is a formal regulatory authorisation. Only a holder of a valid AML in the appropriate category has the legal right to sign the Maintenance Release — the entry in the aircraft's technical log that certifies a maintenance task is complete and the aircraft is airworthy. Without that signature from an AML holder, no commercial aircraft can legally depart. Every flight operated by every airline in Europe is, in this sense, dependent on the AML system.

Because the AML is issued against the EASA regulatory framework — specifically Commission Regulation (EU) No 1321/2014 Annex III (Part-66) — it is recognised by competent authority across all EASA member states without the need for conversion or re-examination. An AML issued in Latvia carries identical privileges in France, Germany, Spain, or any other EASA member country. This makes it one of the most genuinely portable professional licences available in any technical discipline.

The licence is issued with one or more category designations corresponding to the type of maintenance the holder is qualified to certify. Each category requires a distinct training and examination pathway, and each carries its own scope of privileges. Type ratings — endorsements specifying the particular aircraft types the engineer can certify — are added to the licence as the engineer gains approved training and experience on each type.

Privileges by category

Part-66 defines four licence categories. They differ in the scope of maintenance they authorise, the level of responsibility they confer, and the training and experience required to obtain them. Understanding the differences is essential for anyone planning their route through the profession.

Category	Title	Scope of privileges	Maintenance Release authority
A	Mechanic	Line maintenance only. The Category A licence authorises the holder to carry out minor scheduled maintenance tasks and simple defect rectification within the limits of a specific authorisation granted by a Part-145 organisation. The scope is defined by a list of specific tasks — the engineer may only certify work that falls within that task list. Work is carried out under the oversight of a B1 or B2 certifying engineer who retains overall responsibility for the Maintenance Release. Category A is typically the starting point for those entering commercial line maintenance and gaining initial on-the-job experience.	No independent Maintenance Release. Certifies only the specific tasks listed in the Part-145 organisation's authorisation, under the supervision of a B1 or B2 engineer.
B1	Technician-Mechanic	Line maintenance on mechanical and structural systems, including the replacement of avionic line replaceable units (LRUs) and the completion of avionics tests where that work does not require in-depth avionics testing or troubleshooting. B1 covers the full scope of an aircraft's mechanical systems: airframe structures, engines, APU, hydraulics, fuel, pneumatics, flight controls, landing gear, environmental control, ice and rain protection, fire protection, and all associated mechanical systems. The B1 licence is the most common category in commercial airline line maintenance and the category for which the largest volume of employment exists.	Full independent Maintenance Release authority for mechanical scope maintenance on the specific aircraft types endorsed on the licence.
B2	Technician-Avionics	Line maintenance on avionics and electrical systems — flight management computers, autopilot and autothrottle systems, navigation and surveillance equipment (ILS, VOR, DME, ADS-B, TCAS), communications systems, EFIS displays, in-flight entertainment, electrical generation and distribution, and electrical wiring. B2 engineers carry out the avionics-specific tasks that B1 engineers are not authorised to certify independently. As aircraft become increasingly software-defined and dependent on complex integrated avionics architectures, the B2 category is growing in strategic importance across the industry.	Full independent Maintenance Release authority for avionics and electrical scope maintenance on the specific aircraft types endorsed on the licence.
C	Base Maintenance Engineer	Base maintenance — heavy checks, major structural inspections (C-checks, D-checks), significant modifications, and component overhauls carried out in an approved maintenance facility with the aircraft out of service. Category C authorises the return-to-service of the whole aircraft following base maintenance, rather than individual task certifications. To obtain a Category C licence on aeroplanes above 30 tonnes, an engineer must have held a B1 and/or B2 licence as a certifying engineer for at least five years. Category C is typically held by senior engineers in MRO operations and airline technical departments, and it is a prerequisite for the most senior engineering roles in the industry.	Full return-to-service authority for the whole aircraft after base maintenance. The highest level of individual certifying authority available under Part-66.

For career entrants, the decision between B1 and B2 is the primary fork in the road. B1 suits those drawn to mechanical systems, engines, and structural work — the physical, hands-on maintenance of the aircraft as a mechanical object. B2 suits those with a background in electronics, electrical engineering, or computing, and those who want to work with the increasingly complex digital systems that modern aircraft depend on. Both lead to the same level of independent authority and the same strength of employment market. TRITECH's Part-147 approval covers basic training programmes for both B1.1 (turbine aeroplanes) and B2 category licences.

Type rating endorsements on the AML

An AML issued in a given category — B1 or B2 — does not by itself authorise the holder to certify maintenance on any specific aircraft. Before the engineer can sign a Maintenance Release on a particular type, their licence must carry a type rating endorsement for that aircraft. The type rating specifies both the aircraft type and the engine variant, where more than one engine is approved for the airframe.

Type rating endorsements are added to the AML after the engineer completes two things: an approved type rating course on the aircraft, and a period of on-the-job experience on that type under the oversight of an already-endorsed engineer. The type rating course is delivered by a Part-147 approved organisation — such as TRITECH — and covers the aircraft's systems in the depth required by the Part-66 type rating syllabus. Theoretical instruction is typically followed by a practical on-aircraft element, conducted on an actual aircraft of the relevant type at a maintenance facility. The experience requirement ensures that the engineer has applied that knowledge in a real maintenance context before exercising independent certifying authority.

The type rating endorsement is entered directly on the face of the AML. An engineer can accumulate multiple type ratings over the course of their career — many senior engineers hold endorsements for five or more aircraft types. Each additional type rating represents an extension of the engineer's marketable capability and a meaningful increase in their flexibility across the job market.

TRITECH holds Part-147 approval for type rating training on five major commercial and business aviation types: the Airbus A318/A319/A320/A321 family (CFM56 and IAE V2500 engine variants), the Boeing 737-600/700/800/900 NG (CFM56), the BAe 125 / Hawker series 750/800XP/850XP/900XP, the Embraer EMB-135/145, and the Embraer EMB-545/550 (Phenom 300). For engineers targeting commercial airline line maintenance, the A320 family and B737 NG represent the two most strategically valuable first endorsements given the scale of those fleets in European operations.

International validity

The EASA AML is one of the most internationally portable professional licences in any technical field. Within the European Union and the wider EASA member state area — currently comprising 31 states including all EU member states plus Iceland, Liechtenstein, Norway, and Switzerland — an AML issued in any one member state carries full recognition in all others. An engineer licensed by the Civil Aviation Agency of Latvia holds exactly the same privileges working in France, Germany, Ireland, or any other EASA country as they do in Latvia. There is no conversion process, no re-examination, and no additional administrative steps required to exercise the licence across national borders.

Beyond the EASA area, the AML benefits from a growing network of bilateral aviation safety agreements between the EU and non-EU states. These bilateral agreements create working arrangements that simplify or eliminate the re-licensing process for EASA-licensed engineers working in jurisdictions including the United States (through the EU-US BASA), the United Kingdom (through post-Brexit UK CAA arrangements), Canada, Brazil, and a number of others. The specific terms of each bilateral arrangement vary, and engineers should verify current requirements with the relevant authority, but the overall trajectory has been toward increasing mutual recognition of the EASA AML as the international standard for maintenance licensing.

For engineers with ambitions to work internationally — whether in the Gulf region's major MRO hubs, in Asia-Pacific's expanding aviation market, or in transatlantic corporate aviation — the EASA AML is the strongest possible foundation. Major MRO operators and airlines in regions without their own bilateral arrangements with EASA frequently accept it as demonstrating the competence standard required for their own local licensing processes, reducing the time and cost of conversion.

Applying for the AML

Once all the regulatory requirements are satisfied — module examinations, basic training hours, on-the-job experience, and type rating training — the engineer applies to the competent national aviation authority for issuance of the AML. In Latvia, this is the Civil Aviation Agency (Civilās aviācijas aģentūra). The application package submitted to the authority includes the Certificates of Recognition for each passed Part-66 module, evidence of basic training hours (where applicable), documented and verified on-the-job experience records, the type rating course completion certificate, and the application form prescribed by the authority.

The authority reviews the submitted documentation against the Part-66 requirements and, where satisfied, issues the AML. The licence is a formal regulatory document and is renewed or revalidated periodically in accordance with national authority procedures. Engineers are responsible for maintaining the validity of their licence throughout their career, including compliance with any continuing qualification or refresher requirements imposed by the authority or their employer.

For engineers trained at TRITECH, the documentation package is compiled progressively throughout the training programme. Each passed module generates an immediate CofR; type rating completion generates a course completion certificate accepted by the authority. TRITECH's administration team is experienced in supporting candidates through the application process and can advise on the specific documentation requirements of the Latvian Civil Aviation Agency.