Aerospace glossary

Plain-English definitions of the aviation and aerospace terms used across Aerospace Garage — 437 terms in 24 domains.

Airlines and markets

• A

  ACMI (wet lease) — Leasing an aircraft together with its crew, maintenance and insurance, usually for a short period.
• Aerodrome — Any defined area used for aircraft to take off, land and move; an airport is an aerodrome with facilities for passengers or cargo.
• Air cargo volume — Tonnes of freight and mail carried or handled in a period.
• Air traffic control (ATC) — The service that keeps aircraft safely separated in the air and on the ground.
• Airport passengers (passengers handled) — Passengers arriving, departing and transferring at a country's or an airport's terminals in a period.
• Airside — The part of an airport beyond security, including the apron and runways.
• ANSP — Air navigation service provider: the organisation running a country's air traffic control.
• AOC (Air Operator Certificate) — The licence a national aviation authority issues to let a company carry passengers or cargo for money.
• AOG (Aircraft on Ground) — An aircraft grounded until a part or repair arrives; the most urgent call in maintenance and supply.
• Apron (ramp) — The area where aircraft park, load and refuel.
• ASK (available seat kilometres) — One seat flown one kilometre, sold or not; the standard measure of airline capacity.
• Average fleet age — The mean age of the airliners an airline or region operates; older fleets need more heavy maintenance.

• B

  Backlog — Aircraft ordered but not yet delivered.
• Block hour — Time from when an aircraft leaves the gate to when it arrives at the next one; the basic unit of airline cost and pay.
• Business jet — An aircraft built to carry small groups of executives or private passengers.

• C

  CASK — Cost per available seat kilometre; how airlines compare their unit costs.
• Codeshare — Two airlines selling seats on the same flight under their own flight numbers.
• Concession — The right granted to a company to operate an airport or service for a set number of years.
• CTK (cargo tonne-kilometres) — One tonne of cargo carried one kilometre; the standard measure of air cargo traffic.

• D

  Deliveries — New aircraft handed over by a manufacturer to customers in a period.
• Domestic market demand — Passenger demand on flights within one country, measured in RPKs.
• Dry lease — Leasing an aircraft without crew; the airline that leases it operates it under its own licence.

• F

  Fatal accident — An accident in which at least one person on board dies; counted here for commercial airliners only.
• Fifth freedom — The right for an airline to carry passengers between two foreign countries on a flight that starts or ends in its home country.
• Flag carrier — A country's main, often state-linked, airline.
• Freighter — An aircraft built or converted to carry cargo only.

• G

  Greenfield airport — An airport built on a new site rather than by expanding an existing one.
• Gross orders — New aircraft orders placed in a period, before cancellations are subtracted.
• Ground handling — Services on the ground: baggage, loading, refuelling, pushback and passenger handling.

• H

  Hub — An airport where an airline concentrates its connections.

• I

  ILS — Instrument landing system: ground radio guidance for landing in poor visibility.

• J

  Jet fuel price (US$/bbl) — The market price of jet fuel in US dollars per barrel (159 litres); fuel is an airline's largest single cost.

• L

  Load factor — The share of seats (or cargo space) actually sold on a flight or across a network.
• Low-cost carrier (LCC) — An airline built around low fares, one aircraft type and extra charges for services.

• M

  Mid & Emerging Markets — The nine regions Aerospace Garage covers: Gulf and Middle East; North Africa; Sub-Saharan Africa; South Asia; Southeast Asia and the Pacific Islands; China and South Korea; Central Asia, the Caucasus and Mongolia; Türkiye and Eastern Europe; Latin America and the Caribbean.

• N

  Narrow-body (single-aisle) — An airliner with one aisle, such as the A320 family, 737 or C919.
• Net margin — Profit after all costs and taxes as a share of revenue.

• O

  On-time performance (OTP) — The share of flights arriving within 15 minutes of schedule.
• Orbital launch — A rocket launch that places a payload into orbit around the Earth.

• P

  P2F conversion (passenger-to-freighter) — Rebuilding an ageing passenger aircraft as a freighter.