A–Z of Aviation: The Ultimate Glossary by Bostonair

Cut through the jargon. Understand the industry.

In the aviation world, acronyms are everywhere. From the flight line to the boardroom, they’re part of the everyday language—but not always easy to decode. At Bostonair, we work across MRO, CAMO, engineering, and leasing support, so we’ve pulled together this friendly, reliable A–Z of the most-used aviation terms to help you stay fluent in the language of the skies.

Whether you’re a seasoned professional, new to aviation, or supporting the industry from a commercial angle, this glossary will help you navigate the shorthand we all rely on.

🔠 A–Z Glossary

A

AOG – Aircraft on Ground

An urgent situation where an aircraft is unfit to fly. Bostonair’s global teams are often called in for AOG support to minimise downtime and get aircraft safely back in the air.

A-Check – Line Maintenance Inspection

A routine check performed roughly every 400–600 flight hours. It’s usually done overnight and keeps aircraft in top condition between heavier checks.

AOC – Air Operator Certificate

The legal approval for an airline to operate commercial flights. Without it, you’re grounded.

AML – Aircraft Maintenance Licence

A certification that authorises an individual to perform and certify aircraft maintenance. These licences, typically structured under EASA Part-66 or equivalent frameworks, are divided into categories (e.g., A, B1, B2, C) reflecting different levels and types of maintenance authority.

ATC – Air Traffic Control

Maintaining order in the skies by managing the safe and smooth flow of air traffic.

B

BFE – Buyer-Furnished Equipment

Items an airline purchases directly—like galley inserts or seating—that are then installed by the OEM during aircraft assembly.

Base Maintenance

More in-depth work carried out in hangars—think C-checks and D-checks. It’s one of Bostonair’s core services, supported by our engineering and logistics teams.

C

CAMO – Continuing Airworthiness Management Organisation

A certified team responsible for keeping aircraft legally airworthy. Bostonair’s CAMO division works with operators and lessors worldwide to manage compliance and maintenance records.

C-Check – Intermediate Maintenance Check

A detailed inspection performed every 18–24 months. It involves systems checks, inspections, and minor repairs.

CMM – Component Maintenance Manual

OEM-published instructions for how to inspect, test, and repair individual aircraft components.

CT – Continuation Training

CAA – Civil Aviation Authority

the regulatory body responsible for aviation safety and policy in the UK. Bostonair’s approvals align with UK CAA Part 145.

D

D-Check – Heavy Maintenance Visit

The most thorough inspection—done every 6–10 years. The aircraft is essentially dismantled and rebuilt. Bostonair supports these major overhauls with skilled manpower and tooling support.

DMI – Deferred Maintenance Item

A fault that doesn’t pose an immediate safety issue, but still needs to be addressed within a defined timeframe.

E

EASA – European Union Aviation Safety Agency

Europe’s aviation regulator. Bostonair’s approvals align with EASA Part 145 and CAMO requirements.

EIS – Entry Into Service

When an aircraft officially joins a fleet and starts flying commercially. It’s the finish line of aircraft acceptance, often supported by CAMO and lessor teams.

EWIS – Electrical Wiring Interconnecting Systems

ETOPS – Extended-Range Twin-Engine Operational Performance Standards

F

FOD – Foreign Object Debris

Anything on a runway or ramp that shouldn’t be there—tools, stones, trash—and can pose a hazard to aircraft.

FDR – Flight Data Recorder

One of the “black boxes,” recording technical data from each flight.

FTS – Fuel Tank Safety

G

GSE – Ground Support Equipment

Tugs, GPUs, belt loaders—all the gear needed to service an aircraft on the ground.

GVI – General Visual Inspection

A visual check of the aircraft’s structure and components, usually part of routine maintenance.

H

HUD – Head-Up Display

Flight-critical data displayed directly in the pilot’s line of sight, improving situational awareness.

Hangar Check

A catch-all term for any aircraft maintenance done inside a hangar—can range from routine work to full C- or D-checks.

HF – Human Factors

I

IFR – Instrument Flight Rules

Flying based on instruments (rather than visual cues), essential in poor weather or busy airspace.

IATA – International Air Transport Association

Sets commercial and safety standards for airlines worldwide.

J

JAR – Joint Aviation Requirements

Predecessor to EASA standards, still referenced in older certifications and documentation.

K

KPI – Key Performance Indicator

A common term in maintenance contracts and leasing. Bostonair uses KPIs to track turnaround times, quality, and on-time delivery.

L

LOPA – Layout of Passenger Accommodations

A diagram showing how seating and safety features are arranged in the cabin.

LESSOR – Aircraft Owner or Financing Entity

Owns the aircraft and leases it to an operator. Bostonair supports lessors during lease transitions, redeliveries, and audits.

LLP – Life-Limited Part

A part that can only be used for a specific number of cycles or hours before mandatory replacement.

Line Maintenance – Life-Limited Part

Quick-turn maintenance performed directly on the aircraft line covering routine checks, defect rectification, and on-call support to keep aircraft flying safely and efficiently. It’s one of Bostonair’s core services, backed by our skilled engineers and dedicated logistics teams.

M

MRO – Maintenance, Repair & Overhaul

The sector of aviation focused on keeping aircraft airworthy. Bostonair is a trusted MRO service provider across Europe and beyond.

MEL – Minimum Equipment List

Specifies which systems can be inoperative without grounding the aircraft—critical for safe but efficient operations.

N

NDT – Non-Destructive Testing

Techniques like ultrasound or X-ray used to check aircraft parts for damage without taking them apart.

NOTAM – Notice to Air Missions

Time-sensitive notices that alert flight crews to changes in airport operations, hazards, or temporary restrictions.

O

OEM – Original Equipment Manufacturer

Builds the aircraft or its components. Bostonair engineers work closely with OEM specifications during maintenance and modification projects.

OPS – Operations

The team that plans flights, manages crews, and keeps things running day-to-day.

OTP – On Time Performance

key performance indicator that measures a flight’s punctuality.

P

PNR – Passenger Name Record

The digital file that holds a passenger’s travel itinerary.

PBN – Performance-Based Navigation

Advanced navigation that allows aircraft to fly more direct routes with precision.

PAX – Passengers

An aircraft passenger refers to any person on board an aircraft who is being transported from one location to another, excluding members of the flight crew and cabin crew.

Q

QAR – Quick Access Recorder

Like the FDR, but allows for quicker data retrieval—useful for operational monitoring.

R

RTS – Return to Service

The final stamp of approval confirming that an aircraft or part is ready to fly again. A key milestone in Bostonair’s MRO workflows.

RAMS – Reliability, Availability, Maintainability, Safety

A framework used to evaluate aircraft system performance and serviceability.

S

SB – Service Bulletin

Recommendations from OEMs for inspections or upgrades. They’re not always mandatory, but often improve safety or efficiency.

STC – Supplemental Type Certificate

Approves a change to the original aircraft design—like new seating layouts or avionics upgrades.

T

TAT – Turnaround Time

The time it takes to service and dispatch an aircraft between flights. At Bostonair, we focus on keeping TATs short without compromising quality.

TCAS – Traffic Collision Avoidance System

An onboard system that alerts pilots to nearby aircraft, helping prevent mid-air collisions.

TDR – Technical Dispatch Reliability

A metric that measures the percentage of flights that depart on schedule without technical delays or cancellations.

U

ULD – Unit Load Device

Standard containers used to efficiently load cargo into an aircraft’s hold.

UAS – Unmanned Aircraft System

Commonly known as drones. Increasingly used for inspections in hard-to-reach aircraft areas.

V

V-Speeds – Velocity Speeds

Critical speeds for take-off, landing, and safety (like V1, VR, and V2). Every pilot knows them by heart.

W

W&B – Weight and Balance

Calculations done before every flight to ensure the aircraft is loaded safely.

Winglet

A small upward curve at the end of the wing that improves fuel efficiency by reducing drag.

X, Y, Z

Not too many aviation terms here (yet)—but if you’ve got a good one, let us know and we’ll add it.