Part-66 Aircraft Maintenance Licence (AML)

The Aircraft Maintenance Licence (AML) is the EASA licence that qualifies an individual to certify aircraft maintenance. It is established by Annex III to Commission Regulation (EU) No 1321/2014, the part of the continuing-airworthiness framework known simply as Part-66. Holding a Part-66 licence is what allows a person to act as certifying staff and issue a Certificate of Release to Service (CRS) — the legal statement that maintenance has been completed correctly and the aircraft, or a component, is fit to return to service.

Part-66 divides the licence into categories that reflect the type and depth of work the holder may certify. Category A is the line mechanic category: it permits release to service after minor scheduled line maintenance and simple defect rectification, within the limits of the specific tasks the holder is authorized for. Category B1 is the mechanical technician category, covering aircraft structure, powerplant, and mechanical and electrical systems. Category B2 is the avionics technician category, covering avionic and electrical systems. Category B2L is a lighter avionics licence limited to aircraft other than large aeroplanes and organized around system ratings such as communications/navigation, instruments, and autoflight. Category B3 covers piston-engine non-pressurized aeroplanes of 2,000 kg maximum take-off mass (MTOM) and below. Category C is the base maintenance category, allowing the holder to issue a single Certificate of Release to Service for a complete aircraft after base maintenance, drawing on the work of B1 and B2 support staff. Category L is the category for sailplanes and lighter craft, covering sailplanes and powered sailplanes, balloons and airships, with sub-categories reflecting composite and non-composite construction.

Earning and using an AML rests on three pillars. First, basic knowledge: applicants must pass the Part-66 basic knowledge examination modules appropriate to their category, covering subjects from mathematics and physics through to specific airframe, engine, and avionics disciplines. Second, experience: applicants must accumulate a minimum period of practical maintenance experience, with the required duration depending on the category and on whether the applicant has completed approved training. Third, type ratings: the basic licence alone does not permit a holder to certify a specific aircraft type. For larger aircraft, an aircraft type rating must be endorsed on the licence following approved type training and, where required, on-the-job training, before the holder can sign for that type.

Part-66 does not stand alone. The licence is the personal qualification, but certification privileges are exercised within an approved maintenance organization under Part-145 (or under the lighter Part-CAO regime for smaller organizations), which grants the individual their certification authorization. Part-66 basic and type training is delivered by maintenance training organizations approved under Part-147. Together, Part-66, Part-145, and Part-147 form the personnel, organization, and training legs of the EASA maintenance system, and they operate under the continuing-airworthiness umbrella of Part-M and Part-CAMO.

The FAA equivalent of the AML is the Airframe and Powerplant (A&P) mechanic certificate. Both authorize the holder to perform and approve maintenance, but the systems differ in structure: the A&P is issued in two broad ratings (Airframe and Powerplant) without EASA's finer B1/B2 mechanical/avionics split, and the FAA relies less on formal per-type ratings on the certificate itself, whereas the Part-66 licence carries specific aircraft type ratings that gate what the holder may certify.

For a flight school that maintains its own fleet, or that runs a combined training and maintenance operation, Part-66 defines who may legally sign off its aircraft. Every entry into service after maintenance depends on an appropriately licensed and authorized person issuing the Certificate of Release to Service. Understanding which category and type ratings the school's certifying staff actually hold — and keeping those qualifications current — is essential to keeping the fleet legally airworthy and available for training.

Because the licence is built from basic knowledge, experience, and type ratings, tracking it is a genuine administrative task. A school must know each engineer's category, which aircraft types are endorsed on their licence, and when any continuation or recency requirements fall due. A gap — an expired authorization or a type rating that does not cover a newly added aircraft — can quietly ground an aircraft or, worse, lead to a release to service being signed by someone without the correct privileges.

Aviatize's Maintenance Control and Maintenance Execution modules connect the work being done on an aircraft to the qualified person who certifies it, so a Certificate of Release to Service is tied to a named individual whose Part-66 category and type ratings are on record. This keeps the certifying-staff qualification visible at the moment it matters — when work is signed off.

Aviatize's Digital Data & Records module holds each engineer's licence details, category, and type ratings alongside the aircraft records, so the school can see at a glance whether it has appropriately licensed certifying staff for every type in its fleet and flag qualifications that need attention before they lapse.