Airworthiness Directive (AD)

An Airworthiness Directive (AD) commonly refers to a legally enforceable instruction issued by a civil aviation authority to correct an unsafe condition in an aircraft, aircraft engine, propeller, or related appliance. It identifies a specific safety issue and states the required action, such as inspection, modification, repair, replacement, operating limitation, or recurring checks.

An AD is not the same as a general maintenance recommendation, a service bulletin, or an internal quality notice. It is an external regulatory directive that applies to defined products, configurations, serial number ranges, or operating conditions.

Where it applies

In aerospace manufacturing, repair, and sustainment workflows, an AD can affect production records, maintenance planning, configuration control, parts traceability, and document revision management. Organizations may need to determine whether delivered or serviced units are affected, verify compliance status, and maintain evidence showing what action was taken and when.

ADs are most often associated with aircraft in service, but they can also affect upstream manufacturers, suppliers, and MRO providers when product design, approved parts, instructions for continued airworthiness, or repair activity are involved.

What an AD typically includes

• The affected product or population

• The unsafe condition being addressed

• The required corrective action or limitation

• The compliance time or recurring interval

• References to supporting technical information, where applicable

Common confusion

Airworthiness Directive vs. Service Bulletin: a service bulletin is typically issued by the manufacturer and provides technical instructions or recommended actions. An AD is issued by the regulator and makes specified action mandatory for affected products within its jurisdiction.

Airworthiness Directive vs. internal NCR/CAPA: an NCR or CAPA addresses quality issues inside an organization’s quality system. An AD addresses an unsafe condition in the aviation regulatory context and may trigger internal quality or configuration actions, but it is not itself an internal quality record.

In regulated operations

Within digital manufacturing and MRO systems, AD handling is commonly tied to serial number effectivity, maintenance lineage, approved documentation, and evidence retention. For example, an ERP, MES, PLM, or MRO platform may be used to identify affected assemblies, route required work, and preserve the traceable record of completion.