Aviation regulation comes with its own language. This glossary explains the terms you’ll see across our coverage — in plain English, without the legal density of the original rule text. Each entry is short on purpose. Click any term to jump straight to it.
A
Acceptable Means of Compliance (AMC) A method that EASA has pre-approved for meeting a specific rule. It is not the only way to comply. It is simply one way the regulator has already accepted.
Advisory Circular (AC) FAA guidance that explains how to meet a rule. It is not legally binding. Operators can follow it, or propose another method that achieves the same safety result.
Air Operator Certificate (AOC) The licence a company needs to run commercial flights. No AOC means no legal commercial operation, regardless of how good the aircraft or crew are.
Airworthiness Directive (AD) A mandatory order from a regulator. It tells operators to inspect, repair, or modify an aircraft, engine, or part. ADs exist because a real safety problem was found. Compliance is not optional.
Airworthiness Review Certificate (ARC) An EASA document confirming an aircraft remains safe to fly. It follows a formal review of the aircraft’s records and condition. It must be renewed on a set schedule.
Alternative Method of Compliance (AMOC) A different way to satisfy an Airworthiness Directive. The operator proposes it. The regulator must approve it before it can be used in place of the original instruction.
C
CAMO (Continuing Airworthiness Management Organization) An EASA-approved organisation that manages an aircraft’s ongoing safety. It plans maintenance, keeps records, and makes sure the aircraft stays compliant between major inspections.
Certification Specification (CS) EASA’s technical design standards. An aircraft, engine, or part must meet the relevant CS before it can be certified for use in Europe.
Compliance Date The date by which a new rule must be followed. Miss it, and the operator is in violation — even if the aircraft is otherwise safe.
D
Design Approval Holder (DAH) The company that holds official approval for an aircraft or part’s design. They are responsible for that design’s continued safety, even years after manufacture.
Double Opt-In Not an aviation term, but one you’ll see if you subscribe to our newsletter. It means we ask you to confirm your email address before sending anything else. This keeps spam out of your inbox and keeps our list clean.
E
EASA (European Union Aviation Safety Agency) The regulator responsible for civil aviation safety across the EU. It sets design standards, certifies aircraft, and oversees national aviation authorities within the bloc.
eVTOL (Electric Vertical Takeoff and Landing) An aircraft that takes off and lands like a helicopter but runs on electric power. Regulators are still building dedicated rules for this category, since it doesn’t fit neatly into existing airplane or helicopter rules.
F
FAA (Federal Aviation Administration) The US regulator for civil aviation. It certifies aircraft, licenses pilots, and issues the rules that govern US airspace and US-registered aircraft.
Final Rule A regulation that has completed the public comment process and is now legally binding. Once its effective date passes, operators must comply.
G
Guidance Material (GM) Explanatory material from a regulator that helps interpret a rule. Like an Advisory Circular, it is not legally binding on its own.
I
ICAO (International Civil Aviation Organization) A United Nations agency that sets global aviation standards. Individual countries then write their own rules based on ICAO’s recommendations.
Instructions for Continued Airworthiness (ICA) The manufacturer’s manual for keeping an aircraft or part safe over its working life. It covers maintenance schedules, repair limits, and inspection requirements.
M
Means of Compliance (MOC) Any accepted method for proving a design meets a safety rule. Every certification rule needs at least one MOC before an aircraft or part can be approved.
Maintenance Organization Approval Official recognition that a repair facility meets the standards needed to maintain aircraft. Without it, a shop cannot legally perform certified maintenance work.
N
Notice of Proposed Amendment (NPA) EASA’s version of a draft rule, published for public comment before it becomes final. The FAA equivalent is an NPRM.
Notice of Proposed Rulemaking (NPRM) The FAA’s draft of a new rule. The public can comment for a set period — usually 60 to 90 days — before the FAA finalises it.
P
Part 121 / Part 135 (FAA) The two main US rule sets for commercial flying. Part 121 covers scheduled airlines. Part 135 covers smaller commercial operators, like charter and air taxi services.
Part-M / Part-145 (EASA) EASA’s equivalent rule sets. Part-M covers continuing airworthiness management. Part-145 covers approved maintenance organisations.
S
SAF (Sustainable Aviation Fuel) A jet fuel substitute made from renewable sources. Regulators are introducing blending mandates that require airlines to use a rising percentage of SAF over time.
Special Airworthiness Information Bulletin (SAIB) An FAA notice that flags a potential safety concern. Unlike an AD, it is not mandatory — but it often signals that an AD may follow.
T
Type Certificate (TC) The core approval that confirms an aircraft design meets all applicable safety standards. Every aircraft model needs one before it can be manufactured and sold.
U
UK CAA (UK Civil Aviation Authority) The regulator for civil aviation in the United Kingdom. Since Brexit, it operates independently from EASA, though many of its standards remain closely aligned.
UAS (Unmanned Aircraft System) The formal regulatory term for what most people call a drone. It includes the aircraft itself plus the equipment used to control it.
Note: This glossary will expand over time. If there’s a term you’d like explained, contact us — we’re always adding to this list.