There is a confusion that has run through hangars for decades: treating an Airworthiness Directive and a Service Bulletin as variations of the same document. They are not. The difference between the two is the difference between law and advice — and mixing them up is costly in both directions.
The hierarchy in one sentence
The Airworthiness Directive (AD, or DA — Diretriz de Aeronavegabilidade — in Brazil) is mandatory. It is issued by the authority — ANAC, FAA, EASA — when an unsafe condition is identified on the type. In Brazil, the subject is covered by RBAC 39. Failing to comply with an applicable AD is not an administrative pending item: the aircraft is no longer airworthy.
The Service Bulletin (SB) belongs to the manufacturer. It is the technical communication that recommends an inspection, modification or replacement. By itself, it does not compel — the operator evaluates and decides, according to its maintenance program.
And here lies the catch that sustains the confusion: many ADs are born from SBs. The authority identifies that the condition described in the bulletin is critical and turns it into a directive — sometimes ordering compliance with the SB itself, within a deadline it sets. The document that was a recommendation yesterday became an obligation with a date. Whoever doesn't follow the transition finds out at the audit.
The two classic mistakes
Treating an SB as an AD. The operator complies with every bulletin as if it were mandatory, without evaluating applicability and relevance to its operating profile. The cost is direct: maintenance the operation didn't require, an aircraft on the ground without regulatory need.
Treating an AD as an SB. The reverse is much worse. "Leave it for the next inspection" works for a recommendation, not for a directive with a deadline. An overdue AD brings down the airworthiness of the entire aircraft — and it is among the first things an audit or a pre-purchase inspection checks.
The operational problem: finding out in time
The conceptual part is simple. The real problem is logistical: how does your operation find out that a new AD has been issued for your type?
The traditional flow depends on someone remembering to look: visiting the authorities' websites, filtering by model, interpreting applicability by serial number, cross-checking with current hours and cycles. It is recurring, technical work that is easy to postpone — and an AD doesn't warn you when it falls due. The operation that discovers a directive six months after it was published flew six months in a condition the authority had already declared unsafe.
How Alis handles this
Alis's CTM (Maintenance Tracking — Controle Técnico de Manutenção) attacks exactly the logistical part:
- Directive search at the official source: the platform consults the airworthiness publications by aircraft type, instead of waiting for someone to remember to look.
- AI-assisted triage: on top of the raw result, the AI generates a summary, prioritization and next steps for the technical team — what is urgent, what depends on serial number, what is already covered.
- The decision remains technical and human — and that is deliberate: the AI organizes and prioritizes, but does not decide applicability or compliance. Airworthiness judgment is the responsibility of whoever holds the prerogative, and a serious tool respects that boundary.
- From directive to due date: the applicable AD enters the due-date control along with everything else — hours, cycles, calendar — and is alerted like any CTM item, not kept in a parallel folder.
The result is the inversion that matters: instead of the operation chasing the directive, the directive comes to the operation — with context, priority and deadline in the same place where maintenance is already controlled.
If your technical tracking still lives in a spreadsheet, it is worth starting with why Excel breaks down in CTM — directive management is a chapter of the same problem.
This article is informational and does not replace current regulations. The applicability and compliance of Airworthiness Directives must be evaluated by a qualified professional, in accordance with RBAC 39 and the authorities' official publications.