Airworthiness Directives and Service Bulletins

What an Airworthiness Directive Is

An airworthiness directive is a legally enforceable FAA rule that orders specific action on an aircraft, aircraft engine, propeller, or appliance. The regulations call each of these a product. The FAA issues an airworthiness directive when it finds that an unsafe condition exists in a product and that the condition is likely to exist or develop in other products of the same type design. The directive then specifies the inspections, conditions, and limitations that must be met, and any actions that must be taken, to resolve the unsafe condition.

Airworthiness directives sit on the binding side of the line between regulations and advisory material, a distinction covered in how FAA regulations are organized. The legal framework for the system is 14 CFR Part 39, and the directives are regulations issued to correct an unsafe condition in a product.

Who Must Comply With an Airworthiness Directive

Anyone who operates a product that does not meet an applicable airworthiness directive is in violation of the regulation. The violation recurs: the requirement is broken each time the aircraft is operated or the product is used while the directive’s requirements remain unmet.

Responsibility starts with the owner or operator. For most aircraft, the owner or operator is primarily responsible for maintaining the aircraft in an airworthy condition, including compliance with Part 39. An airline or other Part 121 certificate holder carries primary responsibility for the airworthiness of its aircraft, and arranging for another company to do the maintenance does not relieve it of that responsibility. The wider question of who answers for what is covered in who is responsible for aviation safety.

“Operate” covers more than piloting. It includes causing or authorizing the use of the aircraft for air navigation, whether or not the person holds legal control as owner, lessee, or otherwise. Compliance is also due at the time or date written into the directive, not at the next scheduled inspection. Maintenance providers carry their own duty: a person who performs a 100-hour, annual, progressive, or other required inspection must determine that applicable airworthiness requirements are met, including compliance with airworthiness directives.

How the FAA Issues an Airworthiness Directive

The FAA uses one of three paths, chosen by urgency. The most common is a notice of proposed rulemaking, which invites public comment and is followed by a final rule that takes the comments into account. When an unsafe condition warrants adoption without prior notice, the FAA issues a final rule with request for comments, which takes effect on the date the directive states and is open to comment afterward. For the most urgent conditions, the FAA issues an emergency airworthiness directive directly to affected owners and operators.

An emergency directive reaches people in two steps. It is effective on the date received by owners and operators the FAA notifies directly, and the FAA then publishes a Federal Register version with the same requirements that is effective for those who did not receive notice.

Emergency Airworthiness Directives in Practice

In November 2025 the FAA used the emergency path for the Boeing MD-11. Emergency Airworthiness Directive 2025-23-51, issued November 8, 2025, applied to all MD-11 and MD-11F airplanes. It prohibited further flight until each airplane was inspected and all applicable corrective actions were performed using a method approved by the manager of the FAA’s Continued Operational Safety Branch. The FAA issued it after an accident in which the left engine and its pylon, the engine’s mounting structure, detached from the airplane during takeoff.

The Federal Register version was published November 14, 2025, effective December 1, 2025 for those not already notified, with comments due December 29, 2025. The same day the FAA issued Emergency Airworthiness Directive 2025-23-53, which replaced the first directive, kept its requirements, and extended them to the Model MD-10-10F and MD-10-30F and to several DC-10 models. The Federal Register version, published November 24, 2025, estimates that the directive affects 167 airplanes of U.S. registry. It describes the cause of the detachment as under investigation and calls the directive an interim action.

Those documents show the requirements as of their issue dates. The current status of any airworthiness directive, including whether a later one has revised or replaced it, is checked in the Federal Register and the FAA’s online airworthiness directive records.

Where to Find an Airworthiness Directive

The FAA publishes airworthiness directives in full in the Federal Register as amendments to 14 CFR 39.13. They are part of the Code of Federal Regulations but are not codified in the annual edition, so the Federal Register and the FAA’s online document system are the places to look. The FAA lists emergency directives, final and proposed rules for airworthiness directives, and the Airworthiness Directive Biweekly report as document types searchable in the FAA’s Dynamic Regulatory System, and offers email delivery of new directives and special airworthiness information bulletins by aircraft type and make.

Alternative Methods of Compliance

The method written into an airworthiness directive is not always the only acceptable one. Anyone may propose an alternative method of compliance or a change in the compliance time if the proposal provides an acceptable level of safety, and may use it only if the manager of the FAA office named in the directive approves. If a change to the product affects the ability to do what the directive requires, the owner or operator must request that approval. Each directive identifies the office responsible for approving alternatives. The November 2025 MD-11 emergency directive, for example, names the branch manager of the Continued Operational Safety Branch as holding that authority.

Service Bulletins and Advisory Notices

A service bulletin is a manufacturer’s document that conveys service information to owners and operators, such as modifications or inspections. It is not an airworthiness directive, and a manufacturer’s statement that a bulletin is mandatory, without more, does not make it so.

A bulletin becomes mandatory in specific ways. First, an airworthiness directive can incorporate it by reference. The service document then becomes part of the directive, and compliance with an incorporated bulletin or portion of one is mandatory. If the two conflict, the directive controls. A directive that only mentions a bulletin as a further source of information does not make the bulletin’s actions required. Second, a maintenance program can require it. For a Part 91 owner who adopted a manufacturer’s recommended inspection program, the FAA concluded in a legal interpretation that later-issued bulletins are not mandatory unless an airworthiness directive or other FAA rule requires them. That reasoning may not apply to programs used under Parts 121 and 135, which can require compliance with later-issued manufacturer bulletins.

A special airworthiness information bulletin is a different tool. The FAA uses these bulletins to alert, educate, and make recommendations, and they contain non-regulatory information that does not meet the criteria for an airworthiness directive.

Records of Airworthiness Directive Compliance

Maintenance records are where the mandatory line shows up on paper. For most registered aircraft, 14 CFR 91.417 requires records of the current status of applicable airworthiness directives, including the method of compliance, the directive number and revision date, and the next due time for any recurring action. Part 121 certificate holders must keep the same kind of directive status record, with the date and method of compliance. These records are retained and transferred with the aircraft when it is sold, and must be made available for inspection by the FAA and by authorized representatives of the NTSB.

Neither rule lists service bulletin status as a separate required record. Work done under a bulletin appears the way other maintenance does, as a description of the work performed or a reference to the data used. When an NTSB investigation or any later review reads those records, whether a bulletin was mandatory is answered by its legal source, an airworthiness directive that incorporated it or a maintenance program that adopted it, and not by the label on the document.