Fatigue Regulation in Aviation Maintenance
Every time a commercial aircraft departs, somewhere in its recent history a licensed engineer signed a release to service.
Their personal Part-66 licence number.
Their authorisation.
Thier professional accountability on the line.
That signature carries enormous weight, and the regulatory framework surrounding it is more sophisticated than most passengers, and many industry professionals outside of maintenance, realise.
EASA Part-145 requires approved maintenance organisations to embed Human Factors training as a condition of approval under 145.A.30(e). EASA Part-66 requires HF knowledge as a baseline qualification for every certifying engineer.
Safety Management Systems are mandatory.
Fatigue risk is explicitly referenced in AMC1 145.A.47(b), which requires organisations to develop and maintain a policy for managing fatigue-related risks as part of their production planning framework.
The regulatory intent is clear.
The industry understands the science.
And yet a meaningful gap exists between what the framework requires on paper and what happens at 3am during an AOG event.
The regulatory asymmetry
Flight crew operating under EASA regulations are subject to Flight Time Limitation rules, specifically Regulation (EU) No 83/2014, which sets hard caps on flight duty periods, cumulative hours, and mandatory rest requirements.
These are not advisory. They are enforceable limits with no individual opt-out. A pilot cannot simply agree with their employer to waive them.
A licensed maintenance engineer operates under a fundamentally different framework.
The EU Working Time Directive (2003/88/EC) sets a 48-hour average weekly maximum, but crucially, it permits individual opt-out agreements. Under Article 22, a worker may consent in writing to exceed the limit.
The consent must be voluntary, and the worker cannot be penalised for refusing.
In practice, in a sector where AOG pressure, overtime culture, and staffing shortages are structural rather than exceptional, the cultural reality and the legal protection rarely align.
There is no equivalent for maintenance engineers.
No hard cap.
No regulatory body monitoring cumulative hours worked across a rolling period.
The organisation is required to have a fatigue policy, but the management of that policy is local, the risk assessment is often delegated to the individual, and the decision to accept or decline a task on fatigue grounds sits, in practice, with the engineer who is already fatigued enough to be making that assessment.
Where the accountability lands
The internal authorisation granted to a licensed engineer under a Part-145 approved organisation is built on an assumption: that the holder understands the regulations, the human factors principles, and the safe working requirements that underpin the privileges they exercise.
It assumes fitness to work. It assumes the system around them is functioning as designed.When it is not, the question of where accountability sits becomes important.
An engineer who certifies an aircraft airworthy while knowingly unfit, through deliberate negligence, carries personal liability.
But an engineer who misses something because the system placed them in conditions of cumulative fatigue, inadequate rest, or sustained pressure occupies a very different position.
The organisation that created those conditions, rather than the individual who worked within them, bears the responsibility.
That distinction matters because the culture of personal licence accountability, entirely appropriate in its proper context, can be misapplied as a pressure mechanism.
Engineers carry the psychological weight of individual responsibility every day.
The signature is personal.
The consequences feel personal.
But the framework that is supposed to protect them from conditions that compromise their performance has a structural gap that the regulatory community has not yet closed.
The reporting culture problem
EASA’s Just Culture framework, embedded within SMS requirements across Part-145 organisations, exists precisely to encourage reporting of safety concerns including fatigue and fitness-for-duty issues.
The principle is that individuals should be able to raise concerns without fear of punitive consequence, provided they are acting in good faith.In practice, fatigue reporting in maintenance remains significantly underused.
The reasons are well understood within the industry:
AOG pressure creates an environment where raising a concern feels like failing the team.
Overtime is financially significant for engineers whose primary salary has not kept pace with the cost of living.
And the absence of a hard regulatory cap means there is no objective threshold an engineer can point to when deciding whether their situation is reportable.
Flight crew have that threshold. Maintenance engineers do not.Human Factors training teaches engineers to recognise the conditions that compromise performance.
Frameworks such as the Dirty Dozen, the twelve most common contributors to maintenance error including fatigue, pressure, and lack of assertiveness, and the SHELL model, which maps the relationship between people, their environment, hardware, software, and other people, are embedded in Part-66 syllabi and Part-145 training programmes.
Engineers know the theory.
The gap is that the regulatory structure does not give them the hard reference point needed to act on it when the pressure is highest.
The dual role dimension
A separate but related issue is emerging across the European MRO sector in 2026.
A growing number of licensed engineers are working parallel roles: a permanent position on the hangar floor, supplemented by contract work, freelance consulting, or their own business, to maintain a standard of living the primary salary no longer supports.
This is not captured by any regulatory framework.
An engineer who works 40 hours in a Part-145 organisation and then works further hours in a separate capacity during their notional rest period is not in breach of any aviation-specific regulation.
Their organisation’s fatigue policy covers what happens within the organisation’s visibility.
What happens outside it is outside the framework entirely.
The irony is substantial. We require Human Factors training.
We mandate SMS. We teach the science of fatigue-induced error.
And then we leave an unregulated space around the working lives of the people whose cognitive performance is most safety-critical in the entire maintenance chain.
What needs to change
The industry is not short of awareness. It is short of structural accountability.
A meaningful step forward would be an FTL-equivalent framework for maintenance engineers: not necessarily identical to flight crew limitations, but a set of hard regulatory minimums governing cumulative duty hours, mandatory rest periods, and the conditions under which overtime can and cannot be applied.
Such a framework would give engineers an objective reference point for fitness-for-duty decisions, give organisations a clear compliance obligation, and give regulators visibility of a risk that is currently unmonitored at the systemic level.Until that conversation happens formally, the gap between what the Human Factors framework intends and what the regulatory structure actually enforces will remain.
The engineers know the gap exists.
The question is whether the people who can close it are paying attention.
OAT provides training across aviation maintenance, human factors, and safety management.
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