Aviation glossary

From A to Z · 235

A

Manufacturing and maintenance

A, B, C and D checks

Packages of scheduled maintenance, rising in depth from A to D, that an aircraft undergoes at set intervals of flight hours, cycles or calendar time.

Safety

Accident

Occurrence linked to the operation of an aircraft in which someone is fatally or seriously injured, the aircraft suffers major structural damage or it goes missing.

Safety

Accident investigation authority

Independent state body that investigates aviation accidents and serious incidents to establish what happened and prevent it from happening again.

Operations and flight

ADS-B

Automatic Dependent Surveillance–Broadcast

A system in which an aircraft automatically and regularly broadcasts its satellite-derived position, altitude, speed and identity by radio.

The aircraft

Aileron

Movable surface near each wingtip; deflected in opposite directions on the two wings, the ailerons roll the aircraft about its longitudinal axis.

Operations and flight

Air traffic control

The service that keeps aircraft safely apart and orders traffic on the ground and in the air through clearances and instructions passed by radio.

The aircraft

Aircraft family

Group of models from one manufacturer that share a basic design, flight deck and systems while differing in size, capacity or range.

On Vuelopedia

Aircraft key

The unique identifier Vuelopedia gives each aircraft, made up of its model family and serial number, which stays the same when the registration changes.

On Vuelopedia

Aircraft record

The Vuelopedia page devoted to one individual aircraft, bringing together its identity, technical data, operators, flight log and event history.

Registration and rules

Aircraft register

Official record kept by each state of the aircraft entered on it, listing their registration, type, serial number and owner.

On Vuelopedia

Aircraft status

An aircraft's situation according to the available evidence: active, stored, retired, scrapped or, where the evidence is insufficient, unknown.

Airlines and business

Airline

Company that carries passengers, cargo or mail by air for payment, holding an air operator certificate issued by its national aviation authority.

Airlines and business

Airline alliance

Partnership of airlines that coordinate their networks, frequent flyer programmes, lounges and connections to give passengers a joined-up journey.

Airlines and business

Airline group

Holding company that brings several airlines under one owner, with each usually keeping its own brand, operating certificate and airline codes.

Airports

Airport elevation

Height above mean sea level of the highest point of an aerodrome's landing area, given in feet and metres.

Registration and rules

Airworthiness directive

Mandatory instruction issued by an aviation authority to correct an unsafe condition found in a type of aircraft, engine or component.

Airports

Alternate airport

Airport to which an aircraft can proceed if landing at the intended destination becomes impossible or inadvisable, specified in the flight plan.

Operations and flight

Approach

The phase of flight in which the aircraft lines up with the runway and descends along a defined path to the point where the crew decides to land or go around.

Airports

Apron

Area of an airport where aircraft park to board and disembark passengers, load cargo, refuel and receive line maintenance.

The aircraft

APU

Auxiliary Power Unit

Small gas turbine, usually in the tail cone, that supplies electrical power and compressed air when an aircraft's main engines are shut down.

Airlines and business

ASK

Available Seat Kilometres

Measure of an airline's capacity: the number of seats available for sale multiplied by the kilometres flown by each, totalled over a period.

The aircraft

Autopilot

System that holds or changes an aircraft's flight path, altitude, heading and vertical speed according to values selected by the crew.

B

Safety

Bird strike

Collision between an aircraft and one or more birds in flight, which happens mostly at low altitude during take-off, initial climb and approach.

Operations and flight

Block time

The total time of a flight, measured from when the aircraft leaves the departure gate until it stops at the arrival gate, including taxiing and any holding.

Registration and rules

Boeing customer code

Two-character code that Boeing assigned to each customer and added to the model designation, as in the 747-436 built for British Airways.

Engines

Bypass ratio

Ratio between the mass of air that flows around a turbofan's core through the outer duct and the mass that passes through the core to be burnt.

C

The aircraft

Cabin classes

Service levels into which an airline divides its cabin, such as first, business, premium economy and economy, each with its own seats and service.

The aircraft

Cabin configuration

Interior layout an operator chooses for its aircraft: seat count, classes, seats per row, seat pitch, galleys and lavatories.

Operations and flight

Cabin crew

Crew members responsible for passenger safety in the cabin and for in-flight service, as distinct from the flight crew who fly the aircraft.

Manufacturing and maintenance

Cabin retrofit

The renewal of an in-service aircraft's interior with new seats, entertainment, lighting or a different layout of cabin classes.

Airlines and business

Cabotage

Carriage of passengers or cargo between two points within the same country, traffic that most states reserve for their own airlines and close to foreign carriers.

Registration and rules

Call sign

Name by which an aircraft is identified in radio communications with air traffic control, such as Speedbird or Lufthansa followed by the flight number.

Airlines and business

Cargo airline

Airline dedicated to carrying freight, operating freighter aircraft rather than passenger flights, either on its own account or on behalf of other companies.

The aircraft

Cargo hold

Cargo compartment, usually located beneath the cabin floor, that carries checked baggage, freight and mail on a passenger aircraft.

Registration and rules

Certificate of airworthiness

Document issued by the state of registry to an individual aircraft, confirming that it conforms to its approved design and is in a condition for safe operation.

Airlines and business

Charter airline

Airline selling non-scheduled flights hired by a customer, such as a tour operator, company or government, that books the whole aircraft for a trip.

Registration and rules

Chicago Convention

International treaty signed in 1944 that sets out the principles of international civil aviation and gave rise to ICAO.

Registration and rules

Civil aviation authority

Public body that regulates and oversees a country's civil aviation: it registers aircraft, issues licences and certifies airlines and airports.

Operations and flight

Climb

The phase in which an aircraft gains height after take-off up to its cruising level, following a published departure route and the levels cleared by ATC.

Airlines and business

Codeshare

Agreement under which an airline sells seats, under its own code and flight number, on a flight operated by another carrier.

The aircraft

Combi

Aircraft that carries passengers and cargo together on the main deck, separated by a partition, and fitted with a large cargo door.

Engines

Combustor

Section of a turbine engine where compressed air is mixed with fuel and burnt continuously, producing the hot gases that drive the turbine.

Engines

Compressor

Section of a turbine engine that raises the pressure of incoming air through successive rows of rotating blades and fixed vanes before it reaches the combustor.

Airports

Control tower

Air traffic control unit based at an airport that clears take-offs, landings and ground movements and handles traffic in the immediate vicinity.

Airports

Coordinated airport

Airport where capacity falls short of demand, so landing or taking off there requires a slot allocated by an independent coordinator.

Operations and flight

Cruise

The central and usually longest phase of a flight, in which the aircraft flies level at its most efficient height and speed between the climb and the descent.

Weights and performance

Cruise speed

Speed at which an aircraft flies most of a journey, in level flight at high altitude, chosen to balance fuel burn, time and cost.

Safety

CVR

Cockpit Voice Recorder

Flight recorder that captures the pilots’ voices, radio communications and flight deck sounds, from aural warnings to engine noise.

D

Manufacturing and maintenance

Delivery

The handover of a new aircraft from its manufacturer to the customer, an airline or a lessor, after acceptance checks and final payment.

Registration and rules

Deregistration

Cancellation of an aircraft's entry on a state's register, for example because it is exported to another country, withdrawn from use or scrapped.

Operations and flight

Descent

The phase in which an aircraft leaves its cruising level and loses height in a controlled way until the start of the approach to its destination.

Manufacturing and maintenance

Desert storage

The parking of out-of-service aircraft in arid regions, where low humidity slows corrosion and land and space come cheap.

Operations and flight

Diversion

A decision to land at an airport other than the planned destination, because of bad weather, a runway closure, a medical emergency on board or a technical problem.

On Vuelopedia

Documented existence

Vuelopedia's level of evidence based on a freely licensed photograph showing an aircraft's registration on an airframe of the model given in its record.

Airlines and business

Dry lease

Lease of an aircraft alone, without crew or maintenance; the lessee airline flies it with its own staff and under its own operating certificate.

E

Registration and rules

EASA

European Union Aviation Safety Agency

European Union agency responsible for civil aviation safety, which certifies aircraft, engines and components and harmonises rules across Europe.

The aircraft

Elevator

Movable surface on the trailing edge of the horizontal stabiliser that raises or lowers the nose, controlling the aircraft's pitch attitude.

Safety

Emergency landing

Landing made with priority because of an emergency on board, usually at the nearest suitable airport and with rescue services standing by.

The aircraft

Empennage

Tail assembly of an aircraft, made up of the horizontal and vertical stabilisers and their control surfaces, providing stability and control.

Manufacturing and maintenance

End of production

The point at which a manufacturer delivers the last example of a type and closes its assembly line, usually once the order backlog has run dry.

Weights and performance

Endurance

Maximum time an aircraft can stay airborne on the fuel it carries, as opposed to range, which measures the distance it can cover.

Engines

Engine core

Central part of a turbofan, essentially the high-pressure compressor, combustor and high-pressure turbine, through which the air that is burnt passes.

Manufacturing and maintenance

Engine overhaul

A visit by an engine to the workshop, after thousands of hours on the wing, to strip it down, inspect it, replace parts and restore its performance.

Manufacturing and maintenance

Entry into service

The date on which a new aircraft type starts carrying fare-paying passengers or revenue cargo with an airline, usually its launch customer.

Operations and flight

ETOPS

Extended-range Twin-engine Operations

Rules that let twin-engine aircraft fly routes far from suitable diversion airports, up to a maximum one-engine flying time approved for each aircraft type and airline.

Safety

Evacuation

Rapid, orderly exit of an aircraft’s occupants through the emergency exits, often by escape slide, when staying on board is more dangerous.

On Vuelopedia

Event record

Each significant fact on file in an aircraft's life: an incident, an accident, a period of storage, a return to service or its scrapping.

F

Registration and rules

FAA

Federal Aviation Administration

United States government agency that regulates the country's civil aviation, certifies aircraft and provides air traffic control services.

Engines

FADEC

Full Authority Digital Engine Control

Computer system that controls every aspect of a turbine engine's operation, including fuel flow, starting and limits, based on the thrust lever position.

Engines

Fan

Large bladed rotor at the front of a turbofan that accelerates the incoming air and generates most of the engine's thrust.

Safety

FDR

Flight Data Recorder

Flight recorder that continuously logs hundreds of aircraft parameters, such as altitude, airspeed, heading, control positions and engine thrust.

Operations and flight

Ferry flight

A flight without passengers or paying cargo that moves an aircraft to where it is needed: another base, a maintenance shop, a new operator or storage.

Manufacturing and maintenance

Final assembly line

The facility where the major sections of an aircraft, often built at other plants, are joined and its systems installed until it is ready to fly.

Safety

Final report

Document with which an investigation authority closes a case: it reconstructs and analyses the facts, sets out causes and factors, and makes recommendations.

Airports

FIR

Flight Information Region

Block of airspace of defined dimensions within which flight information and alerting services are provided, under the responsibility of a given state.

Airlines and business

Firm order and option

Ways in which an airline or lessor orders aircraft: a firm order is a binding contract, while an option reserves a delivery slot that can be confirmed later.

Manufacturing and maintenance

First flight

The moment an aircraft leaves the ground for the first time, whether it is the first example of a new type or an individual production airframe.

Operations and flight

First officer

The pilot who shares the controls with the captain, ranks next in the chain of command and usually sits in the right-hand seat of the flight deck.

Airlines and business

Flag carrier

Airline historically identified with a particular country, often founded or part-owned by its government, and representing that country on international routes.

The aircraft

Flap

Movable surface on the trailing edge of the wing that extends to increase lift at low speed during take-off and landing.

Manufacturing and maintenance

Flight cycles

A unit of aircraft use equal to one take-off and one landing; the main measure of fatigue in the fuselage and in many engine parts.

The aircraft

Flight deck

Forward compartment from which the pilots fly the aircraft and manage its systems, navigation and communications.

Manufacturing and maintenance

Flight hours

The time an aircraft, engine or pilot accumulates in flight; one of the basic measures for scheduling maintenance and for recording experience.

Operations and flight

Flight level

An altitude expressed in hundreds of feet and referenced to the standard pressure of 1013.25 hPa, giving aircraft at height a shared vertical reference.

On Vuelopedia

Flight log

A year-by-year summary of an aircraft's activity on Vuelopedia: main airport, most-flown routes, number of flights and periods on the ground.

Registration and rules

Flight number

Combination of an airline code and a number of up to four digits that identifies a particular air service in timetables, tickets and airports.

Operations and flight

Flight plan

Details of a flight filed with air traffic services before departure: aircraft, route, level, speed, estimated times, destination and alternate airports.

Safety

Flight recorders

Crash-protected units that record flight data and flight deck sounds so that investigators can reconstruct what happened during an occurrence.

Manufacturing and maintenance

Flight test campaign

The series of test flights through which a manufacturer shows the authorities that a new aircraft type meets the requirements for certification.

The aircraft

Fly-by-wire

Flight control system in which the pilot's inputs travel as electrical signals to computers that move the control surfaces.

Safety

FOD

Foreign Object Debris / Foreign Object Damage

Any loose object that does not belong where aircraft operate and could damage them, such as bolts, stones or tools; the term also covers the damage it causes.

Weights and performance

Foot

Imperial unit of length equal to 0.3048 metres, in which civil aviation expresses altitude across most of the world.

The aircraft

Four-engine aircraft

Aircraft powered by four engines, the classic layout for large long-haul airliners before twins took over those routes.

Airlines and business

Freedoms of the air

Set of rights a country grants to foreign airlines to overfly its territory, land there, or carry passengers and cargo to, from and beyond it.

The aircraft

Freighter

Aircraft used solely to carry cargo, with no passenger cabin, a strengthened floor and a large cargo door on the main deck.

Manufacturing and maintenance

Freighter conversion

The rebuilding of a used passenger aircraft as a freighter, with a large side cargo door, a strengthened floor and a cabin stripped to take pallets and containers.

Airlines and business

Frequent flyer programme

Airline loyalty scheme that rewards customers with miles or points redeemable for flights, and with status tiers that bring benefits when travelling.

The aircraft

Fuselage

Main body of an aircraft, carrying the crew, passengers and cargo, to which the wings, tail and landing gear are attached.

G

Airports

Gate

Point in the terminal from which passengers on a flight reach the aircraft, whether by airbridge, on foot across the apron or by bus.

Engines

Geared turbofan

Turbofan with a reduction gearbox between the fan and the turbine that drives it, so that each can turn at its own most efficient speed.

The aircraft

Glass cockpit

Flight deck in which most dial instruments are replaced by electronic screens that combine flight, navigation and systems information.

Operations and flight

Go-around

A manoeuvre in which the pilot abandons an approach or landing, applies power and climbs away to try again or to head for another airport.

Airports

Ground handling

Services an aircraft receives on the ground between flights: passenger handling, baggage, cargo, fuel, cleaning, catering and pushback.

H

Operations and flight

Holding pattern

A racetrack-shaped path that an aircraft flies over a fixed point while waiting for clearance to continue, usually because of congestion or bad weather.

The aircraft

Horizontal stabiliser

Horizontal tail surface that keeps an aircraft stable in pitch and, on most jet airliners, pivots through a few degrees to trim it.

Airlines and business

Hub

Airport where an airline concentrates its flights and times its schedule so that passengers and cargo from many cities can connect with one another.

Airlines and business

Hub-and-spoke

Way of organising an airline network in which most flights start or end at a central airport, where passengers change to reach their destination.

Safety

Hull loss

Accident after which an aircraft is destroyed, goes missing or is so badly damaged that it is not repaired and never returns to service.

I

Registration and rules

IATA

International Air Transport Association

Trade association representing a large share of the world's airlines, which sets common commercial and operational standards for air transport.

Registration and rules

IATA airline designator

Two-character designator that IATA assigns to an airline and that appears in its flight numbers, tickets and reservations, such as BA for British Airways.

Airports

IATA airport code

Three-letter code that IATA assigns to an airport for use on tickets, timetables and baggage tags, such as LHR for London Heathrow.

Registration and rules

ICAO

International Civil Aviation Organization

Specialised agency of the United Nations that sets the standards and recommended practices for international civil aviation.

Registration and rules

ICAO 24-bit address

Unique 24-bit code, written as six hexadecimal characters, that electronically identifies an aircraft in the signals transmitted by its transponder.

Registration and rules

ICAO aircraft type designator

Code of up to four characters that ICAO assigns to each aircraft type for use in flight plans and air traffic control, such as A320 or B738.

Registration and rules

ICAO airline designator

Three-letter designator that ICAO assigns to an aircraft operator for use in flight plans and air traffic control, such as BAW for British Airways.

Airports

ICAO airport code

Four-letter code under the ICAO system that identifies an aerodrome in flight plans, air traffic control and weather reports, such as EGLL for London Heathrow.

Safety

ICAO Annex 13

ICAO’s international standard setting out how civil aviation accidents and incidents are investigated, with the sole aim of preventing future ones.

Safety

Icing

Build-up of ice on an aircraft’s structure, engines or sensors, which reduces lift, increases drag and can corrupt instrument readings.

Operations and flight

IFR and VFR

Instrument Flight Rules / Visual Flight Rules

Two sets of flight rules: visual flight rules (VFR), under which pilots navigate and avoid traffic by looking outside, and instrument flight rules (IFR), based on instruments and ATC.

Airports

ILS

Instrument Landing System

Ground-based radio guidance system that leads an aircraft both laterally and vertically to the runway, allowing landings in very poor visibility.

Airports

ILS categories

Classification of ILS approaches by minimum decision height and visibility, from CAT I to CAT III, which allows aircraft to land in dense fog.

Safety

Incident

Occurrence, other than an accident, associated with the operation of an aircraft that affects or could affect the safety of operation.

Airlines and business

Integrator

Express delivery company that controls the whole chain, from collection to delivery, with its own aircraft and sorting hubs, offering a door-to-door service.

J

Airports

Jet bridge

Enclosed, movable walkway linking the terminal to an aircraft door so that passengers can board and disembark without crossing the apron.

Engines

Jet fuel

Petroleum-based fuel used by the turbine engines of civil aircraft; the most common grades are Jet A-1 and, in the United States, Jet A.

Operations and flight

Jet stream

A narrow band of very strong westerly winds at high altitude in the mid-latitudes, which shortens or lengthens flights depending on whether they fly with it or against it.

Airlines and business

Joint venture

Agreement in which two or more airlines run a set of routes together and share revenue or profit, acting as a single business in that market.

The aircraft

Jumbo jet

Popular nickname for the Boeing 747, the first wide-body airliner, sometimes applied to other very large passenger aircraft.

K

Weights and performance

Knot

Unit of speed used in aviation and at sea, equal to one nautical mile per hour, which is exactly 1.852 km/h.

L

Operations and flight

Landing

The final phase of flight in which the aircraft crosses the runway threshold, touches down on its main gear and slows to taxi speed.

The aircraft

Landing gear

Assembly of legs, wheels, shock absorbers and brakes that supports an aircraft on the ground and absorbs landing loads; on most airliners it retracts in flight.

Airlines and business

Launch customer

First airline or operator to order a new aircraft model in sufficient numbers for the manufacturer to commit to launching the programme.

Airlines and business

Lessor

Company that owns aircraft and rents them out to airlines for years at a time in return for regular payments, without operating them itself.

Registration and rules

Line number

Number showing the order in which an aircraft left its type's assembly line; a convention used mainly by Boeing alongside the serial number.

On Vuelopedia

Live position

The current position of an aircraft in flight, shown in its record from the ADS-B signals it transmits and that ground receivers pick up.

The aircraft

Livery

Paint scheme and markings that identify an aircraft's operator: colours, name, logo and often a distinctive design on the tail.

Airlines and business

Load factor

Share of the capacity offered that is actually sold; for passengers, revenue passenger kilometres divided by available seat kilometres over a flight or period.

Airlines and business

Low-cost carrier

Airline built around keeping costs down to sell cheap fares: a single aircraft type, high aircraft utilisation, one cabin class and extras charged separately.

M

Weights and performance

Mach number

Ratio of an aircraft's speed through the air to the speed of sound in that air; Mach 1 means flying at exactly the speed of sound.

Safety

Mayday and pan-pan

Standard radio calls for declaring an emergency: ‘mayday’ signals grave or imminent danger, ‘pan-pan’ an urgent situation that needs no immediate help.

Weights and performance

MLW

Maximum Landing Weight

Maximum weight at which an aircraft is certified to land, determined mainly by the strength of the landing gear and the airframe.

Manufacturing and maintenance

MRO

Maintenance, Repair and Overhaul

The industry and range of work that keeps aircraft airworthy: line maintenance, heavy checks, engine overhauls and component repairs.

Registration and rules

MSN

Manufacturer Serial Number

Serial number assigned by the manufacturer to each aircraft which, unlike the registration, stays with it unchanged for its entire life.

Weights and performance

MTOW

Maximum Take-Off Weight

Maximum weight at which an aircraft is certified to begin its take-off, including structure, crew, passengers, cargo and fuel.

Weights and performance

MZFW

Maximum Zero Fuel Weight

Maximum permitted weight of an aircraft with all its payload, crew and passengers on board, excluding the usable fuel in its tanks.

N

Engines

Nacelle

Streamlined housing around an aircraft engine that brings together the air intake, access cowlings, thrust reverser and exhaust nozzle.

The aircraft

Narrow-body

Airliner with a single cabin aisle and typically four to six seats per row; the most common type on short and medium-haul routes.

Registration and rules

Nationality prefix

Opening letters or digits of a registration that show the country in which an aircraft is registered, such as G for the United Kingdom or N for the United States.

Weights and performance

Nautical mile

Unit of distance used in air and sea navigation, equal to exactly 1,852 metres and corresponding approximately to one minute of arc of latitude.

O

Safety

Occurrence

Umbrella term for any safety-related event in aviation, covering everything from a minor incident to an accident.

Weights and performance

OEW

Operating Empty Weight

Weight of an aircraft ready for service, with crew, equipment and the necessary fluids, but without passengers, cargo or usable fuel.

Airlines and business

On-time performance

Share of flights that depart or arrive within a set margin of their scheduled time, usually meaning less than 15 minutes late.

Engines

Open rotor

Turbine engine whose large blades spin in the open air without a casing, achieving a very high bypass ratio and lower fuel burn than a turbofan.

Airlines and business

Operator and owner

Distinction between the operator, the airline that flies an aircraft and is responsible for its operation, and the legal owner, often a lessor or a bank.

On Vuelopedia

Operator history

The time-ordered sequence of airlines that have operated an aircraft, with the registration it carried with each and, where known, its owner.

Manufacturing and maintenance

Order backlog

The aircraft firmly ordered from a manufacturer but not yet delivered; it shows how many years of production lie ahead.

P

Weights and performance

Passenger capacity

Number of passengers an aircraft can carry, which varies with the cabin layout chosen by the airline and is capped by a certified maximum.

Weights and performance

Payload

Weight of everything that earns revenue on a flight, namely passengers and their baggage, cargo and mail, excluding the aircraft, crew and fuel.

Weights and performance

Payload-range diagram

Chart showing how much payload an aircraft can carry over each distance, revealing the trade-off between payload and fuel within the maximum take-off weight.

Operations and flight

Phases of flight

The stages into which a flight is divided, from leaving one gate to arriving at the next: taxi, take-off, climb, cruise, descent, approach and landing.

Operations and flight

Pilot in command

The pilot designated as ultimately responsible for the operation and safety of a flight; at an airline this is the captain, who normally sits in the left-hand seat.

Engines

Piston engine

Internal combustion engine in which pistons, driven by burning a mixture of air and fuel, turn a crankshaft that drives the propeller.

Airlines and business

Point-to-point

Network model in which an airline flies directly between the cities it serves, rather than funnelling connections through a central hub airport.

Safety

Preliminary report

First official document of an accident investigation, setting out the facts established in the opening weeks without drawing conclusions about causes.

Manufacturing and maintenance

Preserved aircraft

A retired aircraft kept intact for its historical value, in a museum, on public display or, in some cases, in flying condition.

The aircraft

Pressurisation

System that keeps the air pressure inside an aircraft higher than outside, so that passengers and crew can breathe normally at high altitude.

Safety

Probable cause

Investigation finding that identifies the event, or combination of events and conditions, that most likely led to an occurrence.

Engines

Propeller

Set of blades with an aerofoil section that, as it rotates, accelerates a large mass of air rearwards to produce thrust for piston and turboprop aircraft.

Manufacturing and maintenance

Prototype

An early example of a new aircraft type, built to prove the design on the ground and in the air before the type is certified.

Operations and flight

Pushback

The manoeuvre in which a tug pushes an aircraft backwards away from the gate, since airliners do not normally reverse under their own power.

Engines

Pylon

Structure that attaches an engine to the aircraft, usually beneath the wing, and carries its thrust as well as fuel lines, wiring and bleed air ducts.

R

Weights and performance

Range

Maximum distance an aircraft can fly without refuelling with a given load, while keeping the fuel reserves required by regulations.

Registration and rules

Re-registration

Change of an aircraft's registration, common when it moves to another country or operator; its serial number, by contrast, never changes.

The aircraft

Regional aircraft

Smaller passenger aircraft, typically with about 30 to 100 seats, designed for short routes and airports with modest traffic.

Airlines and business

Regional airline

Airline flying short, thinner routes with regional aircraft, often linking smaller cities to the hubs of the major carriers.

Registration and rules

Registration

Combination of letters and numbers that identifies an aircraft with the state in which it is registered and must be painted on its exterior.

Manufacturing and maintenance

Retirement

The permanent removal of an aircraft, or of a whole type, from an operator's fleet, whether for sale, conversion, preservation or scrapping.

Manufacturing and maintenance

Return to service

An aircraft's return to operation after storage, repair or maintenance, once it has been confirmed as fit to fly.

Airlines and business

RPK

Revenue Passenger Kilometres

Measure of airline traffic: the number of fare-paying passengers carried multiplied by the distance, in kilometres, that each of them flies.

The aircraft

Rudder

Movable surface hinged to the back of the fin that swings the nose left or right, controlling the aircraft in yaw.

Airports

Runway

Rectangular surface at an aerodrome prepared for aircraft to take off and land, identified by its magnetic orientation.

Airports

Runway designation

Two-digit number painted at each end of a runway giving its magnetic heading in tens of degrees, with L, C or R added where runways are parallel.

Safety

Runway excursion

Event in which an aircraft leaves the runway surface during take-off or landing, either off the side or past the end.

Safety

Runway incursion

Incorrect presence of an aircraft, vehicle or person on the protected area of a surface designated for the landing and take-off of aircraft.

Airports

Runway surface

Material a runway is built from, such as asphalt, concrete, gravel or grass, which determines the aircraft and weights it can accept.

Airports

Runway threshold

Beginning of the part of a runway usable for landing, marked with white longitudinal stripes and green lights visible to aircraft on approach.

S

Engines

SAF

Sustainable Aviation Fuel

Jet fuel made from renewable or waste sources that can be blended with conventional kerosene and reduces carbon dioxide emissions over its life cycle.

Safety

Safety recommendation

Proposal from an investigation authority, based on lessons from an occurrence, to prevent future accidents, with no presumption of blame or liability.

Airlines and business

Sale and leaseback

Deal in which an airline sells an aircraft to a lessor and immediately leases it back, so that it can keep flying the aircraft without interruption.

Airports

Scheduled service

Flight or series of flights operated to a published timetable, open for sale to the public and repeated systematically between two or more points.

Manufacturing and maintenance

Scrapping

The dismantling of a retired aircraft to recover its usable parts and recycle the rest of the structure for its materials.

Safety

Serious incident

Incident whose circumstances indicate there was a high probability of an accident, and which is therefore formally investigated with the same rigour as an accident.

Registration and rules

Service bulletin

Document in which the manufacturer of an aircraft, engine or component recommends an inspection, improvement or modification to its operators.

Weights and performance

Service ceiling

Highest altitude at which an aircraft can operate normally, set either by its ability to keep climbing or by the limit fixed in its certification.

Manufacturing and maintenance

Service life

The period of use, measured in cycles, flight hours and years, over which the manufacturer has shown that an aircraft's structure withstands fatigue.

The aircraft

Slat

Movable leading-edge surface that moves forward to open a slot, letting the wing reach a higher angle of attack before it stalls.

Airports

Slot

Permission to land or take off at a congested airport on a given date and time, or a departure time allocated to manage the flow of air traffic.

Engines

Specific fuel consumption

Amount of fuel an engine burns for each unit of thrust or power it produces over a given time; the standard measure of engine efficiency.

The aircraft

Spoiler

Hinged panel on the upper wing surface that rises to spoil lift and add drag, helping the aircraft descend, slow down or roll.

Operations and flight

Squawk code

A four-digit number, each digit from 0 to 7, that air traffic control assigns to a flight and the transponder transmits to identify it on radar screens.

Manufacturing and maintenance

Storage

The status of an aircraft that stops flying for a time and is parked under a preservation programme while its future is decided.

Safety

Substantial damage

Damage or failure that adversely affects an aircraft’s structural strength, performance or flight characteristics and would normally require major repair.

The aircraft

Swept wing

Wing whose edges angle backwards from the fuselage to delay compressibility effects, allowing an aircraft to cruise closer to the speed of sound.

T

The aircraft

T-tail

Tail layout in which the horizontal stabiliser sits on top of the fin, so that seen from the front or rear the assembly forms a letter T.

Operations and flight

Take-off

The phase in which an aircraft accelerates along the runway to rotation speed, raises its nose and climbs away to a safe height above any obstacles.

Weights and performance

Take-off distance

Distance an aircraft needs from the start of its take-off run until it reaches a reference height above the runway, normally 35 feet for transport aircraft.

Safety

TAWS

Terrain Awareness and Warning System

Onboard system that gives pilots visual and aural alerts when the aircraft’s flight path brings it dangerously close to terrain or obstacles.

Operations and flight

Taxiing

Movement of an aircraft on the ground under its own power between the apron and the runway, along taxiways and following instructions from ground control.

Airports

Taxiway

Paved route linking the runways with the apron and other parts of an airport, along which aircraft move on the ground under their own power.

Safety

TCAS

Traffic Alert and Collision Avoidance System

Onboard system that interrogates the transponders of nearby aircraft and, if it detects a collision risk, tells the pilots to climb or descend.

Airports

Terminal

Airport building where passengers check in, pass through controls, wait for their flight, board and collect their baggage on arrival.

Engines

Thrust

Force produced by an engine as it accelerates air or exhaust gas rearwards, pushing the aircraft forward in reaction.

Engines

Thrust reverser

Engine mechanism that, after touchdown, redirects part of the airflow forwards to help slow the aircraft on the runway.

Operations and flight

Transponder

An on-board device that answers secondary radar interrogations with an identity code, its altitude and, in Mode S, a unique 24-bit address.

Engines

Turbine

Set of bladed wheels that extracts energy from the hot combustion gases to drive the engine's compressor, fan or propeller.

Engines

Turbofan

Jet engine in which a large front fan drives air around the core, producing most of the thrust with greater efficiency and less noise.

Engines

Turbojet

Jet engine in which all the intake air passes through the compressor, combustor and turbine before leaving the nozzle as a high-speed jet.

Engines

Turboprop

Gas turbine engine that drives a propeller through a reduction gearbox, with the propeller rather than the exhaust producing almost all the thrust.

The aircraft

Twin-engine aircraft

Aircraft powered by two engines, now the dominant layout in airline service thanks to the reliability of modern engines.

Registration and rules

Type certificate

Document in which an aviation authority declares that the design of an aircraft, engine or propeller model meets the applicable airworthiness requirements.

U

The aircraft

ULD

Unit Load Device

Standardised container or pallet in which baggage and freight are consolidated so they can be loaded onto an aircraft as a single unit.

Operations and flight

Ultra-long-haul flight

A non-stop flight of exceptional length, usually more than 16 hours, which needs very long-range aircraft and augmented crews who take turns to rest.

V

Operations and flight

V1, VR and V2

Reference speeds calculated for every take-off: V1, the decision speed; VR, the rotation speed; and V2, the safety speed for climbing with an engine out.

The aircraft

Variant

Version of an aircraft model that keeps the basic design but changes features such as length, engines, range or intended role.

On Vuelopedia

Verification seal

A mark showing that an aircraft's identity (registration, serial number and model) has been checked against the official register of its civil aviation authority.

Airports

VOR

VHF Omnidirectional Range

Ground-based radio aid transmitting on VHF that lets an aircraft determine which radial, or magnetic bearing from the station, it is on.

W

Operations and flight

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