Aviation Data Glossary
A reference guide to aviation data terminology used by airlines, airports and operators worldwide.
- Aeronautical charges
- Fees levied by an airport on airlines and aircraft operators for the use of airport infrastructure and services. These are distinct from non-aeronautical revenues such as retail or car parking income.
- See: What are Airport Fees and Charges?, Airports with new Fees and Charges for 2026 - Updated Analysis , Airports with new Fees and Charges for 2026
- Airport Carbon Accreditation (ACA)
- An internationally recognised programme that independently assesses and recognises airports' efforts to manage and reduce their carbon emissions.
- See: RDC’s March 2026 Aviation Emissions Report: Ethiopia, RDC’s February 2026 Aviation Emissions Report: Singapore , RDC’s January 2026 Aviation Emissions Report: United Kingdom, RDC Aviation’s Emissions Methodology Independently Verified by Normec Verifavia
- Available Seat Kilometre (ASK)
- A measure of airline capacity: one available passenger seat flown one kilometre. Used as the denominator when calculating emissions or cost efficiency on a comparable basis across airlines and routes.
- See: RDC’s March 2026 Aviation Emissions Report: Ethiopia, RDC’s February 2026 Aviation Emissions Report: Singapore , RDC’s January 2026 Aviation Emissions Report: United Kingdom, RDC’s December 2025 Aviation Emissions Report: Turkey, Spirit Airlines: Profitability and Future Strategy
- Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA)
- The Carbon Offsetting and Reduction Scheme for International Aviation, a global market-based measure developed by ICAO to address CO2 emissions from international flights. Airlines whose operations fall within scope must monitor, report and verify their emissions annually, and offset any growth above a defined baseline by purchasing eligible emissions units. CORSIA operates in distinct phases: a pilot phase (2021–2023), a first phase (2024–2026) with voluntary state participation, and a mandatory phase from 2027 covering most ICAO member states. It is one of the principal compliance programmes referenced in international aviation emissions reporting, alongside the EU ETS and UK ETS.
- See: RDC’s March 2026 Aviation Emissions Report: Ethiopia, RDC’s January 2026 Aviation Emissions Report: United Kingdom , RDC’s September 2025 Aviation Emissions Report: United Arab Emirates, RDC’s August 2025 Aviation Emissions Report: Iceland
- Conditions of Use
- A document published by an airport setting out all applicable fees and charges and the terms and conditions governing flights operating to and from that airport. Also referred to as a Schedule of Charges and Terms & Conditions of Use.
- See: What are Airport Fees and Charges?
- Effective Perceived Noise in decibels (EPNdB)
- A standardised measure of aircraft noise that accounts for both sound intensity and the duration and tonal characteristics of the noise as perceived by a human listener. EPNdB is the unit used in ICAO aircraft noise certification, with measurements taken at three reference points during certified test flights: lateral (full-power, alongside the runway), flyover (after take-off) and approach (during landing). Each aircraft type and variant has certified EPNdB values for these three points, recorded on its noise certificate. Many airports use the sum of these three values — the cumulative EPNdB level — as the basis for noise-related charges, making it the most common noise charging methodology globally.
- See: How Many Airports Have Noise-Based Charges for Aircraft?
- Emissions baseline
- A reference point against which current emissions levels are compared. In aviation, January to December 2019 is widely used as a pre-pandemic baseline year.
- See: RDC’s March 2026 Aviation Emissions Report: Ethiopia, RDC’s February 2026 Aviation Emissions Report: Singapore , RDC’s January 2026 Aviation Emissions Report: United Kingdom, RDC’s December 2025 Aviation Emissions Report: Turkey
- Emissions compliance programme
- A regulatory framework requiring airlines or other aviation stakeholders to monitor, report, and offset or reduce their CO2 output.
- See: RDC’s March 2026 Aviation Emissions Report: Ethiopia, RDC’s February 2026 Aviation Emissions Report: Singapore , RDC’s January 2026 Aviation Emissions Report: United Kingdom, RDC’s December 2025 Aviation Emissions Report: Turkey
- Emissions per ASK
- The volume of CO2 produced for every available seat kilometre flown. Used to compare the carbon efficiency of airlines and airports on a like-for-like basis regardless of network size.
- See: RDC’s February 2026 Aviation Emissions Report: Singapore, RDC’s January 2026 Aviation Emissions Report: United Kingdom , RDC’s December 2025 Aviation Emissions Report: Turkey
- Environmental charges
- Fees linked to an aircraft’s environmental impact, particularly noise and emissions. Aircraft are typically grouped into categories, with charges varying by their impact level.
- See: What are Airport Fees and Charges?
- European Union Emissions Trading System (EU ETS)
- The European Union Emissions Trading System, a cap-and-trade scheme covering CO2 emissions from flights within the European Economic Area. Airlines operating qualifying flights must surrender allowances equal to their verified emissions each year, with the total number of allowances available capped and reduced over time. The scheme applies to intra-EEA flights and, from 2024, to a phased expansion covering departing flights to certain third countries. Together with CORSIA and the UK ETS, the EU ETS is one of the main compliance programmes shaping aviation's emissions cost base.
- See: RDC’s April 2026 Aviation Emissions Report: Hungary, RDC’s March 2026 Aviation Emissions Report: Ethiopia , RDC’s February 2026 Aviation Emissions Report: Singapore
- Focus city
- An airport at which an airline operates a meaningful base of crew, aircraft and direct routes, but without the scale, banked schedule structure or connecting-traffic emphasis of a full hub. Focus cities typically serve point-to-point demand from the local catchment rather than acting as central transfer points for passengers from other origins. The term is used widely in North American aviation in particular, and is a common way for airlines to describe secondary bases that support network breadth without replicating hub infrastructure.
- See: Avianca’s post-chapter 11 Transformation
- Fuel burn
- The mass of fuel consumed by an aircraft over a given flight, sector or phase of operation, typically measured in kilograms or tonnes. Fuel burn is driven by aircraft type, engine variant, weight, route distance, altitude profile, weather and operational factors such as taxi time and routing efficiency. It is the foundational input for calculating aviation CO2 emissions: emissions are derived by multiplying fuel burn by an ICAO-approved emissions factor (typically 3.16 kg of CO2 per kg of jet fuel). Accurate fuel burn modelling at the individual flight level is what makes credible scope 3 emissions reporting possible for airports.
- See: RDC Aviation’s Emissions Methodology Independently Verified by Normec Verifavia, Tackling Scope 3 Emissions: RDC Launches Groundbreaking Solution for Airports , BA's Costly Detour: Why Flights from Heathrow to Beijing are Being Suspended
- Government passenger taxes
- Taxes applied on a per passenger basis, often varying by destination or travel class. These are imposed by national governments and may apply to all airports within the country or to specific airports. Example of such a tax is UK Air Passenger Duty (APD).
- See: How many countries have Government Taxes for Aviation?, What are Airport Fees and Charges? , The Implications of France's Solidarity Tax Increase
- Great circle distance
- The shortest distance between two points on the surface of a sphere, measured along the arc connecting them. In aviation, great circle distance is the theoretical shortest route between two airports, ignoring airspace restrictions, weather, traffic and operational factors. Actual flown distances are typically longer, as flights are routed via published airways, around restricted airspace and to optimise for wind and fuel efficiency. Great circle distance is widely used as the baseline measure when calculating en-route navigation charges, modelling fuel burn and comparing route lengths on a like-for-like basis.
- See: What is the Cost of Closed Airspace?, What Are Overflight Fees and En-Route Air Navigation Charges? , BA's Costly Detour: Why Flights from Heathrow to Beijing are Being Suspended
- Hub
- An airport that serves as a central connecting point in an airline's network, where flights from multiple origins arrive within a coordinated time window to allow passengers to transfer onto outbound flights to multiple destinations. Hubs enable airlines to serve a wider network of city pairs than direct point-to-point operations would economically support, by aggregating passenger demand through connecting traffic. Major hubs are typically associated with a single dominant carrier or alliance and concentrate a high proportion of that carrier's capacity. Hub-and-spoke networks are characteristic of full-service carriers, whereas low-cost carriers more commonly operate point-to-point networks from bases.
- See: Avianca’s post-chapter 11 Transformation, Iberia’s Strategic Network: A Gateway to Latin America , Lufthansa Group Route Strength, LATAM Airlines: Connectivity in Latin America
- ICAO emissions factors
- Standardised values developed by the International Civil Aviation Organization for calculating the CO2 produced by different aircraft types. These form the basis of internationally recognised emissions calculation methodologies.
- See: RDC Aviation’s Emissions Methodology Independently Verified by Normec Verifavia
- ICAO noise certification chapters
- The successive standards for aircraft noise certification defined by ICAO Annex 16, Volume I, used to classify the noise performance of civil aircraft. Each chapter sets progressively stricter cumulative EPNdB limits, with newer chapters applying to aircraft certified after specified dates. Chapter 2 covered older aircraft now largely retired from commercial service in most regions; Chapter 3 applies to most aircraft certified between 1977 and 2006; Chapter 4 introduced a tighter cumulative margin from 2006; and Chapter 14 applies to aircraft certified from 2017 onwards, with the strictest limits to date. Some airports use chapter classification directly as the basis for noise-related charges, though cumulative EPNdB methodologies are more common.
- See: How Many Airports Have Noise-Based Charges for Aircraft?
- Infrastructure charges
- Fees for using airport facilities such as terminals, check-in areas, baggage systems, and airbridges.
- See: What are Airport Fees and Charges?
- Load factor
- The proportion of available seats on a flight that are occupied by paying passengers, usually expressed as a percentage. Calculated by dividing revenue passenger kilometres (RPK) by available seat kilometres (ASK), load factor is a primary indicator of how efficiently an airline is filling its capacity. It feeds directly into route profitability, emissions per passenger and the RDC CARE Index, since higher load factors spread fixed costs and fuel burn across more passengers, improving both unit economics and per-passenger carbon efficiency.
- See: RDC’s March 2026 Aviation Emissions Report: Ethiopia, RDC’s February 2026 Aviation Emissions Report: Singapore , BA's Costly Detour: Why Flights from Heathrow to Beijing are Being Suspended, Ryanair Q1 Pricing Analysis: Key Apex Insights
- Maximum Take-Off Weight (MTOW)
- The maximum certified weight at which an aircraft is permitted to take off. MTOW is a key variable in airport charge calculations, as many airports base their runway charges, parking charges and other fees on this value. Even within the same aircraft type, MTOW can vary depending on the specific variant and configuration, meaning accurate registration-level data is essential for correct billing.
- See: What Are Overflight Fees and En-Route Air Navigation Charges?, Charging Issues for Airports and Airlines , Q. How Complex Can an Airport’s Charges Be?
- Nitrogen oxides
- A group of reactive gases produced when fuel is burned at high temperatures, predominantly comprising nitric oxide (NO) and nitrogen dioxide (NO2). In aviation, NOx is emitted during all phases of flight but is of particular regulatory concern around airports, where it contributes to local air quality issues and is linked to respiratory health effects. NOx output varies significantly by engine type and operating condition, and is certified by ICAO under defined landing and take-off cycle standards. NOx is the most common pollutant used by airports to apply emissions-based charges on aircraft, either alone or in combination with CO2.
- See: How many airports have noise and emissions-based fees and charges for aircraft?, Q. How Many Airports Have Emissions-Based Charges?
- Parking charges
- Costs associated with parking an aircraft at the airport. These are usually based on the length of time parked and aircraft size or weight.
- See: What are Airport Fees and Charges?
- Passenger charges
- Per passenger fees charged by the airport. These are billed to the airline, which usually incorporates the cost into the passenger’s ticket price.
- See: What are Airport Fees and Charges?, Airports with new Fees and Charges for 2026 - Updated Analysis , Airports with new Fees and Charges for 2026
- RDC CARE Index
- A composite sustainability score developed by RDC Aviation that rates any air route, airline and aircraft combination on a scale of 0 (worst) to 10 (best). The index evaluates fuel burn efficiency, seat capacity and load factor, use of sustainable aviation fuel, participation in emissions compliance programmes such as EU ETS and CORSIA, and whether the carrier offsets its emissions. Published monthly as part of RDC's Aviation Emissions Report, the CARE Index provides a standardised benchmark for comparing airline environmental performance across regions.
- See: RDC’s March 2026 Aviation Emissions Report: Ethiopia, RDC’s February 2026 Aviation Emissions Report: Singapore , RDC’s January 2026 Aviation Emissions Report: United Kingdom
- Runway charges
- Fees imposed by the airport for using runways and taxiways, typically applied when an aircraft lands or arrives.
- See: What are Airport Fees and Charges?, Airports with new Fees and Charges for 2026 - Updated Analysis , Airports with new Fees and Charges for 2026
- Scope 3 emissions
- Indirect greenhouse gas emissions that occur in an airline or airport's value chain but are not directly owned or controlled by that organisation. For airports, Scope 3 covers emissions generated by aircraft taking off and landing at their facilities.
- See: RDC’s February 2026 Aviation Emissions Report: Singapore, RDC’s January 2026 Aviation Emissions Report: United Kingdom , RDC Aviation’s Emissions Methodology Independently Verified by Normec Verifavia
- Sector length
- The distance flown on a single flight segment between two airports, typically measured in kilometres or nautical miles. Sector length is a fundamental variable in airline network analysis: it shapes operating costs (fuel burn scales with distance), aircraft suitability (narrow-body aircraft are uneconomic on very long sectors, wide-body aircraft are inefficient on short ones), fare structures (longer sectors generally support higher absolute fares but lower fares per kilometre) and emissions per available seat kilometre. Average sector length is one of the standard metrics used to characterise an airline's network profile.
- See: Connecting the UK: Inside Loganair’s Network and Profit-Driven Routes, Comparing Low-Cost Airline Market Structure and Fares: Europe vs. U.S , Connecting Europe: Connectivity and Fares at Major European Airports, Iberia’s Strategic Network: A Gateway to Latin America
- Security costs
- Charges applied by the airport to cover the security services it provides, including personnel, screening systems, and related equipment.
- Sustainable Aviation Fuel (SAF)
- A category of jet fuel produced from non-fossil feedstocks such as used cooking oil, agricultural residues, municipal solid waste or synthetic processes using renewable electricity and captured carbon. SAF is chemically similar to conventional jet fuel and can be blended with it for use in existing aircraft and infrastructure without modification. On a lifecycle basis, SAF can reduce CO2 emissions by up to 80% compared with fossil jet fuel, though current global production accounts for less than 1% of total aviation fuel use. SAF uptake is one of the factors evaluated in the RDC CARE Index.
- See: RDC’s April 2026 Aviation Emissions Report: Hungary, RDC’s March 2026 Aviation Emissions Report: Ethiopia
- United Kingdom Emissions Trading Scheme (UK ETS)
- The United Kingdom Emissions Trading Scheme, established in 2021 following the UK's departure from the EU ETS. It operates on broadly similar cap-and-trade principles and covers domestic UK flights, flights from the UK to the EEA, and flights between the UK and Gibraltar. Airlines must surrender allowances each year matching their verified emissions on qualifying routes. The UK ETS is one of the principal compliance programmes referenced alongside CORSIA and the EU ETS in aviation emissions reporting.
- See: RDC’s March 2026 Aviation Emissions Report: Ethiopia
- Wet lease
- A leasing arrangement in which one airline (the lessor) provides an aircraft to another airline (the lessee) together with crew, maintenance and insurance — commonly summarised by the industry acronym ACMI (Aircraft, Crew, Maintenance, Insurance). The lessee pays for fuel, airport charges and other variable costs. Wet leases are typically short-to-medium term and used to add capacity quickly, cover for grounded aircraft, support seasonal peaks or enter new markets without committing to full ownership. They contrast with dry leases, where only the aircraft itself is provided and the lessee supplies crew and operational support.
- See: Iberia’s Strategic Network: A Gateway to Latin America