What Is EASA Part-66? The Aircraft Maintenance Licence, Explained
EASA Part-66 is the European rulebook for licensing the engineers who certify that an aircraft is safe to fly after maintenance. It sets out the licence categories, the 17 knowledge modules you have to pass, and the experience you need. This page is a plain-English overview — what Part-66 is, how the exams work, and how to prepare — with links to the official sources at the bottom.
In short
Part-66 is Annex III to Regulation (EU) No 1321/2014. To get an Aircraft Maintenance Licence (AML) you pass written exams on the relevant modules (pass mark 75%) and complete the required practical experience. The licence then lets you issue a Certificate of Release to Service — the legal sign-off that returns an aircraft to service.
What Part-66 actually is
"Part-66" is the nickname for Annex III of the European continuing-airworthiness regulation, Commission Regulation (EU) No 1321/2014 (kept current by amendments such as Commission Implementing Regulation (EU) 2023/989). It defines the standards an individual must meet to be granted an aircraft maintenance licence and to act as certifying staff.
In practice, holding the right Part-66 licence is what allows an engineer to sign the Certificate of Release to Service (CRS) after maintenance — the document that legally returns an aircraft to flight. Without that sign-off, the aircraft stays grounded.
Who it's for
Aircraft maintenance engineers (AMEs / mechanics) who want to certify work on aircraft.
What it grants
The right to issue a Certificate of Release to Service within the privileges of your category.
How you earn it
Pass the module exams (75%) and complete the practical experience for your category.
The licence categories
Part-66 splits the licence into categories by the type of work and aircraft. The category you choose decides which modules you sit. Here is the plain-English version:
| Category | What it covers |
|---|---|
| A (A1–A4) | Minor scheduled line maintenance and simple defect rectification, on the task you are authorised for. |
| B1 (B1.1–B1.4) | Mechanical — airframe, engines and mechanical/electrical systems. Subdivided into turbine/piston aeroplanes and helicopters. |
| B2 | Avionics — avionic and electrical systems. |
| B2L | A B2 licence limited to specific endorsed system ratings (e.g. comm/nav, instruments, autoflight). |
| B3 | Piston-engine non-pressurised aeroplanes of 2,000 kg MTOM and below. |
| C | Base maintenance — certifying release to service for the whole aircraft after base (heavy) maintenance. |
| L (L1–L5) | Light aircraft — sailplanes, balloons, airships and other light/simple aircraft. |
Want the detail on which category fits your career? See the full licence categories guide →
The 17 basic-knowledge modules
The Part-66 syllabus is built from 17 knowledge modules. You only sit the modules required for your category — not all 17. Tap any module to start practising its questions:
Browse the full module syllabus → | See which modules apply to each category →
How the Part-66 exams work
The basic-knowledge exams follow a single, standard format across every EASA member state (Annex III, Appendix II). The headline rules:
75% to pass
The pass mark is 75% for every module, multiple-choice and essay alike.
3 options, 1 correct
Each multiple-choice question has three answers, one of which is right. No "all of the above".
No penalty marking
Wrong answers don't subtract marks — so never leave a question blank.
Essays in Module 7
Module 7 (Maintenance Practices) adds written (essay) questions alongside the multiple choice. The Module 9 and 10 essays were dropped by Regulation (EU) 2023/989 (from June 2024). See worked essay answers →
Experience: exams aren't enough
Passing the modules is only half the licence. Point 66.A.30 also requires hands-on maintenance experience before the licence is issued. How much depends on your category and whether you trained through an approved (Part-147) course:
| Category | No prior training | Skilled-worker background | After a Part-147 course |
|---|---|---|---|
| A, B1.2, B1.4, B3 | 3 years | 2 years | 1 year |
| B1.1, B1.3, B2 | 5 years | 3 years | 2 years |
Full experience requirements (every category) → | Adding a category to an existing licence →
Part-66, Part-145, Part-147 — what's the difference?
These "Parts" are sister annexes of the same regulation and often get mixed up. The simple rule is Part-66 is about people; the others are about organisations:
Part-66 — the individual licence. Your knowledge, exams and experience as an engineer.
Part-145 — the approval for a maintenance organisation. Licensed engineers exercise their privileges inside an approved Part-145 company.
Part-147 — the approval for a training organisation. A Part-147 course is the fast route to your Part-66 exams and can cut the experience needed.
Where is an EASA Part-66 licence valid?
An EASA Part-66 licence is recognised across all EASA member states — the EU countries plus Norway, Iceland, Liechtenstein and Switzerland. EASA is explicit that Part-66 licences issued outside the EASA system are not automatically recognised within it, and vice-versa.
That said, many national authorities model their own rules on Part-66 and use the same 17 modules and 75% pass mark — so EASA Part-66 study is valid preparation for those exams too, even though the licences themselves are separate:
Also relevant where an EASA Part-66 exam route is delivered locally: Egypt (ECAA) and Nigeria (NCAA).
How to prepare for the EASA Part-66 exams
The exams are knowledge-dense and the 75% pass mark leaves little room for error, so the most effective preparation is practising real exam-style questions until you are consistently above pass standard. Our platform covers all 17 modules for categories A, B1, B2, B2L and B3, with timed quizzes, instant feedback and weak-area tracking.
EASA Part-66 — frequently asked questions
How many EASA Part-66 modules are there?
There are 17 basic-knowledge modules in total. You only sit the modules required for your licence category, not all 17.
What is the pass mark for the Part-66 exams?
The pass mark is 75% for every module. Multiple-choice questions have three options with one correct answer, and there is no penalty marking for wrong answers.
How long are my Part-66 exam passes valid?
A passed basic-knowledge exam is valid for 10 years, giving you time to complete the rest of your modules and the required experience.
Do I need experience as well as the exams?
Yes. Point 66.A.30 requires practical maintenance experience in addition to the exams — from 1 to 5 years depending on your category and whether you completed an approved Part-147 training course.
What is the difference between Part-66 and Part-145?
Part-66 licenses the individual engineer; Part-145 approves the maintenance organisation. A licensed engineer exercises their privileges while working inside a Part-145 approved company.
Is EASA Part-66 study valid for the UK CAA exams?
Yes. The UK retained the same 17 modules, licence categories and 75% pass mark, so EASA Part-66 practice questions are valid preparation for UK CAA Part-66 exams. Several other authorities (CASA, GCAA, DGCA and others) align with Part-66 too.
Sources
The facts on this page come from EASA and the official EU legislation (EUR-Lex), not from forums or third-party providers. You can verify each point directly:
-
EASA — Part-66 FAQ · what Part-66 is, the licence categories and the recognition rules.
easa.europa.eu/en/the-agency/faqs/part-66 -
EUR-Lex — Commission Regulation (EU) No 1321/2014 · the continuing-airworthiness regulation; Annex III is Part-66.
eur-lex.europa.eu/…/CELEX:32014R1321 -
EUR-Lex — Commission Implementing Regulation (EU) 2023/989 · the current amendment setting the module & category matrix (Appendix I) and exam standard (Appendix II).
eur-lex.europa.eu/eli/reg_impl/2023/989/oj/eng -
EASA — Easy Access Rules for Continuing Airworthiness (Regulation (EU) No 1321/2014) · the consolidated, plain-layout version of Part-66 with all amendments.
easa.europa.eu/…/commission-regulation-eu-no-13212014
Information last verified against the sources above: June 2026.
This page is general information to help you prepare, not legal advice. Regulations change — always confirm your own licensing situation with your national aviation authority or EASA before making decisions.