Part-ML Airworthiness Review Checklist: From Maintenance Programme to ARC Renewal

A Part-ML airworthiness review certificate (ARC) is valid for one year and is issued on EASA Form 15c only after a satisfactory airworthiness review (ML.A.901(a)). Renewal goes smoothly when three things have been right all year: a declared or approved aircraft maintenance programme (AMP), inspections done within the annual/100-hour tolerance, and complete records. Where a CAMO or CAO has managed the aircraft throughout, the ARC can instead be extended, up to twice.

This guide is for owners of light aircraft on an EU Member State register, including those living in the UK, and for staff of continuing airworthiness organisations. One caveat: since Brexit the UK has its own CAA regime, and that regime is not covered by the sources used here. Everything below comes from Regulation (EU) No 1321/2014, Annex Vb (Part-ML), consolidated to 22 February 2026, and EASA's continuing airworthiness FAQ.

1. The programme: declared or approved

Each aircraft's maintenance is organised under an AMP (ML.A.302(a)), which is either declared by the owner, where no CAMO or CAO manages the aircraft, or approved by the CAMO or CAO responsible for it. The AMP is based on the minimum inspection programme (MIP) or on the design approval holder's instructions for continuing airworthiness (ICA).

Whichever route applies, the AMP must be kept up to date and must include mandatory items such as repetitive airworthiness directives and the airworthiness limitation section, as EASA's FAQ stresses. The FAQ also points out that Part-ML requires the AMP to be reviewed annually, and that for a declared AMP this is normally done by the person carrying out the airworthiness review.

2. Inspections: intervals and tolerance

The MIP intervals in ML.A.302(d)(1) are:

• Aeroplanes, touring motor gliders and balloons: every annual or 100-hour interval, whichever comes first, with a tolerance of 1 month or 10 hours.
• Sailplanes and powered sailplanes other than TMGs: every annual interval, with a tolerance of 1 month.
• In both cases, the next interval is calculated from the time the inspection takes place.

An illustration using only that rule: a glider's annual inspection falls due on 30 April. Using the one-month tolerance, it is carried out on 20 May. The next annual interval then runs from 20 May, so the following inspection is due by 20 May the next year, not 30 April. EASA's FAQ confirms this reading for Part-ML: when the tolerance is applied, the next interval is counted from the accomplishment date.

Aircraft types outside aeroplanes, sailplanes and balloons have no MIP yet; their AMP must be based on the design approval holder's ICA (ML.A.302(d), final paragraph).

3. The records the reviewer will ask for

The review starts with the paperwork. Under ML.A.305, the logbooks show type, registration, date, total flight time, cycles and landings, and the records show the current status of ADs, modifications and repairs, AMP compliance, life-limited components, mass and balance and deferred maintenance. Each CRS must have been entered within 30 days of the work. If a CAMO or CAO has taken over management, ML.A.307(b) requires the owner to transfer those records to it.

4. Who carries out the review

ML.A.901(b) offers four options: the competent authority; an appropriately approved CAMO or CAO; the approved maintenance organisation while it performs the 100-hour/annual inspection in the AMP; or, for aircraft operated under Part-NCO (and balloons and sailplanes in equivalent situations), independent certifying staff during that same inspection, holding a Part-66 licence rated for the aircraft (or a national qualification where Part-66 does not apply) plus an authorisation from the competent authority.

Inside a CAMO, airworthiness review staff need at least 5 years' continuing airworthiness experience, a Part-66 licence, aeronautical degree or national equivalent (or 5 further years' experience instead), formal maintenance training, and an appropriate position (CAMO.A.310). In a CAO, the experience floor is 1 year for sailplanes and balloons and 3 years for other aircraft, plus a licence or degree, or 2 or 4 extra years respectively (CAO.A.045).

5. During the review

ML.A.903 sets out a documented records review in eleven points, from hours and cycles to noise certificate, followed by a physical survey of the aircraft. The practical rules most often asked about:

1. The review can be brought forward by up to 90 days so that the physical survey coincides with a maintenance check, without losing the review pattern.
2. No ARC is issued while findings are open; EASA's FAQ adds that each corrective action should be verified by the reviewer first.
3. The ARC copy is sent to the Member State of registry within 10 days.
4. Airworthiness review tasks may not be subcontracted.
5. If the review reveals AMP deficiencies, the AMP must be amended; if the reviewer disagrees with the owner's or organisation's amendment, the competent authority decides.

6. Extension in a controlled environment

Instead of a fresh review, a CAMO or CAO may extend the ARC for one year, at most twice in a row (ML.A.901(c)), when the aircraft has been continuously managed by that organisation for the previous 12 months, maintained by approved organisations in that period (pilot-owner tasks released by the pilot-owner or independent certifying staff count), and there is no evidence that it is unairworthy. The extension may be anticipated by up to 30 days.

EASA's FAQ adds two clarifications. First, anticipating an extension by more than 30 days means the new expiry date is one year after the extension, not after the old expiry. Second, the two extensions are intended for the same organisation managing the aircraft since the ARC was issued: an ARC extended once by one organisation cannot be extended a second time by another, because that breaks the controlled environment.

Events that cut an ARC short

ML.A.902 makes the ARC invalid if it is suspended or revoked, if the airworthiness certificate or type certificate is suspended or revoked, or if the aircraft is no longer on a Member State register. Within the EU, ML.A.905 keeps the former ARC valid on a transfer of registration until expiry, except where it was issued by a reviewer holding only a national qualification. Aircraft arriving from outside the EU system follow the import route in ML.A.906.

Pitfalls worth avoiding

• Counting the next annual from the old due date after using the tolerance, rather than from the date the inspection was done.
• Leaving CRS entries unrecorded beyond 30 days, which leaves gaps the reviewer has to chase.
• Changing CAMO between an ARC issue and its extension, then expecting the new organisation to extend it.
• Assuming an approved AMP can be skipped because the owner follows the manufacturer's schedule, without checking every condition in ML.A.302(e).

For specific situations, such as an owner switching CAMO mid-year, you can ask the EASA continuing airworthiness knowledge base directly; each answer points to the provision or FAQ entry it uses.

This guide explains EU law and is not airworthiness advice for a given aircraft. Sources: EUR-Lex and EASA's continuing airworthiness FAQ. The UK CAA regime and EASA's AMC/GM to Part-ML are not in the knowledge base.