In short: this glossary defines 87 terms used in claims under EU261, UK261 and the Montreal Convention, plus the main passenger-rights rules outside Europe. Each definition is short; follow the link for the full rule, the article numbers and the court cases.
A
- ADR (alternative dispute resolution)
-
An independent scheme that decides complaints between passengers and airlines without going to court. In the UK, airlines can join a CAA-approved scheme such as AviationADR or CEDR; it is free for passengers, and a decision you accept binds the airline. You normally apply after 8 weeks without a reply or after a final refusal, and within 12 months of the airline's final response.
More: ADR schemes for airlines
- Air traffic flow management (ATFM) (also: ATFM delay)
-
The system that balances the number of flights against the capacity of airspace and airports. In Europe it is run by EUROCONTROL's Network Manager, which gives flights departure slots when a sector or airport is overloaded. An ATFM delay is the waiting time this causes.
- Air traffic management decision
-
A decision by air traffic control about a particular aircraft on a particular day, such as a late slot or a closed runway. Recital 15 of EU261 treats such decisions as extraordinary circumstances, and UK261 Article 2(o) includes them in its definition – but only for the part of the delay they actually cause.
- ANAC Resolution 400
-
The Brazilian civil aviation agency's rules on general conditions of air transport (13 December 2016), amended in September 2026. They require food after 2 hours, accommodation after 4 hours if an overnight stay is needed, and fixed compensation in SDR for denied boarding, but no fixed cash compensation for delay.
- APPR
-
Canada's Air Passenger Protection Regulations (SOR/2019-150), covering flights to, from and within Canada. For delays within the airline's control they set compensation of up to CA$1,000 from large airlines.
- Arrival time
-
The moment that counts when measuring a delay: when at least one aircraft door is opened and passengers are allowed to leave (Court of Justice, Germanwings, C-452/13). UK261 Article 2(n) uses the same idea – when passengers are permitted to exit the aircraft. Touchdown and arrival at the gate do not count.
- Article 5(3)
-
The clause of EU261 that lets an airline avoid paying compensation if it proves the cancellation (and, through case law, the delay) was caused by extraordinary circumstances that could not have been avoided even if all reasonable measures had been taken. It is the defence airlines cite most often in refusal letters.
- Assimilated law
-
The name UK law has used since the end of 2023 for EU laws that were kept after Brexit, previously called "retained EU law" (Retained EU Law (Revocation and Reform) Act 2023, s.5). UK261 is assimilated law.
More: UK261 explained
- Aviation Services Law (Israel)
-
Israel's 2012 law on compensation and assistance for flight cancellation or change of conditions, covering flights to and from Israel. A delay of 8 hours or more counts as a cancellation; fixed compensation is set in shekels by distance and updated annually.
- AviationADR
-
One of the two main CAA-approved ADR bodies for airline complaints in the UK. The CAA lists it for airlines including easyJet, Ryanair, Wizz Air, TUI Airways, Virgin Atlantic, KLM and Air France.
More: ADR schemes for airlines
B
- Bird strike
-
A collision between an aircraft and a bird. The Court of Justice held in Pešková (C-315/15) that it can be an extraordinary circumstance, but the airline must still show it took reasonable measures, and only the delay the strike actually caused is excused.
- Boarding pass
-
The document that proves you checked in for the flight. Keep it (or a screenshot of the mobile version) with your booking confirmation: together they show you had a confirmed reservation and presented yourself on time, two conditions of EU261 and UK261.
- Burden of proof
-
Who has to prove what. You must show your flight was covered and late, cancelled or overbooked; the airline must prove any extraordinary circumstance, that it took all reasonable measures, and – for cancellations – when it told you (EU261 Article 5(4)).
C
- CAA (Civil Aviation Authority)
-
The UK aviation regulator and the body that enforces UK261. Its Passenger Advice and Complaints Team (PACT) handles complaints about airlines that are not members of an approved ADR scheme.
More: Complaining to the CAA
- Cancellation
-
The non-operation of a flight that was planned and on which at least one seat was reserved (EU261 Article 2(l)). A cancellation notified less than 14 days before departure normally gives a right to compensation, as well as a refund or re-routing and care.
- CAR-PWP
-
The UAE General Civil Aviation Authority's Passenger Welfare Program regulation (Issue 02, applicable from 1 January 2025). It sets care duties for delays, cancellations, diversions and denied boarding at UAE airports, without fixed cash compensation.
- Care (right to care) (also: duty of care)
-
What the airline must give you free while you wait: meals and refreshments in reasonable relation to the waiting time, two phone calls or e-mails, and a hotel with transfers if you have to stay overnight (EU261 Article 9). It starts after 2, 3 or 4 hours depending on distance, and it is owed even in extraordinary circumstances (McDonagh v Ryanair, C-12/11).
More: Flight delay rights
- CEDR
-
The Centre for Effective Dispute Resolution, a CAA-approved ADR body. The CAA lists it for British Airways, BA CityFlyer and Cathay Pacific, among others.
More: ADR schemes for airlines
- Check-in deadline
-
To be protected you must check in by the time the airline gave you or, if none was given, no later than 45 minutes before the published departure time (EU261 Article 3(2)). For a cancelled flight you do not need to turn up at all.
- Claims company (also: claims agency, claim management company)
-
A business that pursues compensation claims for passengers in return for a share of the payout, usually only if the claim succeeds. Using one is optional: you can claim from the airline yourself for free.
More: Claim companies compared
- Community carrier
-
An airline holding an operating licence from an EU Member State (EU261 Article 2(c)). It matters for flights into the EU, which EU261 covers only if a Community carrier operates them.
- Confirmed reservation
-
A booking the airline or tour operator has accepted and registered, shown by a ticket or other proof. It is one of the basic conditions for EU261 and UK261 protection (Article 3(2)).
- Connecting flight (single booking)
-
Two or more flights booked together as one journey. EU261 and UK261 assess them as a whole: the delay is measured at the final destination and the distance is the whole journey (Folkerts, C-11/11; Wegener, C-537/17; UK261 Article 3(1A)).
- Court of Justice of the European Union (CJEU)
-
The EU's highest court on the meaning of EU law. Its rulings – such as Sturgeon on 3-hour delays – bind courts in every Member State. Rulings made before the end of 2020 form part of the case law carried into UK law; UK courts are not bound by later ones but may have regard to them.
More: Case law library
- Crew shortage
-
Not having enough pilots or cabin crew to operate a flight, for example through sickness or poor rostering. It is normally part of the airline's ordinary operations, not an extraordinary circumstance; the UK Supreme Court held in Lipton v BA Cityflyer ([2024] UKSC 24) that a captain falling ill is inherent in an airline's activity.
D
- Deadlock letter
-
The airline's final response refusing your complaint. In the UK it opens the way to ADR (or, if the airline has no ADR scheme, to the CAA), as does 8 weeks without a reply.
More: ADR schemes for airlines
- Delayed baggage
-
A checked bag that arrives later than you do. The Montreal Convention lets you claim reasonable proven costs, such as essentials you had to buy, up to 1,519 SDR; the written complaint must reach the airline within 21 days of getting the bag back.
- Denied boarding (also: bumping)
-
A refusal to carry a passenger who presented for boarding on time with valid documents, except on reasonable grounds such as health, safety or security (EU261 Article 2(j)). If you did not volunteer, you are owed compensation immediately, plus a refund or re-routing and care. There is no extraordinary-circumstances defence.
- Distance band
-
The three distance brackets that set the compensation amount: 1,500 km or less; 1,500–3,500 km (and, under EU261, all intra-EU flights over 1,500 km); over 3,500 km. Under EU261 they pay €250, €400 or €600; under UK261 £220, £350 or £520.
- Diversion
-
A flight that lands at an airport other than the scheduled one. If you reach your final destination 3 hours or more late as a result, you may be owed delay compensation unless the diversion was caused by extraordinary circumstances.
- DOT refund rule
-
The US Department of Transportation's 2024 rule (14 CFR part 260) requiring automatic refunds when a flight to, from or within the US is cancelled or significantly changed and you do not accept the alternative. The US has no federal fixed compensation for delays.
- Downgrade
-
Being moved to a lower class than you paid for. EU261 Article 10 gives a refund of 30%, 50% or 75% of the ticket price for that flight, depending on distance, within seven days.
E
- EU261
-
Regulation (EC) No 261/2004, the EU law that sets common rules on compensation and assistance for denied boarding, cancellation and long delay. It covers flights departing the EU (and Iceland, Norway and Switzerland) on any airline, and flights into the EU on an EU airline.
- EU261 reform (Regulation (EU) 2026/2202)
-
The amending regulation published in the Official Journal on 2 October 2026, applying from 23 October 2027. It keeps the 3-hour threshold and €250 / €400 / €600, and adds a 9-month window for claiming from the airline and a 30-day deadline for the airline to pay or explain a refusal. It does not change UK261.
More: The EU261 reform
- European Small Claims Procedure (ESCP)
-
A simplified written court procedure for cross-border money claims of up to €5,000 between EU countries (Regulation (EC) No 861/2007), started with a standard form (Form A). It is not available to or from the UK since Brexit, and Denmark does not take part.
- Extraordinary circumstances
-
Events that are not inherent in the normal running of an airline and are beyond its actual control – such as weather that makes flying unsafe, air traffic control decisions, security risks or strikes by people outside the airline. If the airline proves one caused the disruption and could not be avoided by all reasonable measures, it does not owe compensation (care is still due).
F
- Final destination
-
The destination on your ticket or, for directly connecting flights, the destination of the last flight (EU261 Article 2(h)). The 3-hour delay is measured here, not at a connecting airport.
- Force majeure
-
A general legal term for events beyond a party's control. EU261 and UK261 do not use it – they speak of extraordinary circumstances, which courts interpret narrowly – but rules outside Europe often do, for example Brazil's ANAC rules and Dubai's 2026 consumer directive.
- Frequent-flyer ticket
-
A ticket paid for with miles or points. EU261 excludes free and reduced fares not available to the public, but expressly covers tickets issued under frequent-flyer and other commercial programmes (Article 3(3)).
G
- Great-circle distance
-
The shortest distance between two airports over the surface of the earth, which EU261 and UK261 use to set the compensation band (Article 7(4)). It is not the distance the aircraft actually flew.
H
- Hotel accommodation
-
Part of the right to care: when a stay of one or more nights becomes necessary, the airline must provide a hotel and transport to and from it (EU261 Article 9(1)(b)–(c)). From 23 October 2027 EU airlines may cap it at three nights where the disruption is due to extraordinary circumstances.
More: Flight delayed overnight
I
- Interpretative Guidelines
-
Guidance from the European Commission summarising how EU261 should be read in the light of the case law, published in 2016 (2016/C 214/04) and updated in 2024 (C/2024/5687). They are not binding law but are widely cited.
- Intra-EU flight
-
A flight between two airports in the EU. Under EU261 every intra-EU flight over 1,500 km falls in the €400 band, even if it is longer than 3,500 km.
J
- Jet2.com v Huzar
-
The 2014 Court of Appeal judgment ([2014] EWCA Civ 791) holding that technical problems, even unforeseen ones, are part of an airline's normal activity and do not excuse a long delay. The CAA still cites it.
More: Case law library
K
- Knock-on delay (also: reactionary delay)
-
A delay caused by a problem on an earlier flight of the same aircraft. An extraordinary circumstance on an earlier rotation can excuse it only if the airline shows a direct link and that it took reasonable measures to limit the effect on later flights.
More: Knock-on delays
L
- Letter before action (also: letter before claim)
-
The final written demand you send before issuing court proceedings. In England and Wales the Practice Direction on Pre-Action Conduct expects one, with a reasonable time to reply (14 days in a simple case).
- Limitation period (also: time limit)
-
The time you have to start court proceedings. EU261 and UK261 set none of their own, so national law applies (Moré v KLM, C-139/11): 6 years in England and Wales and in Northern Ireland, 5 years in Scotland, and different periods in other countries.
More: Time limits by country
- Lost baggage
-
A checked bag the airline admits is lost, or that has not arrived 21 days after it was due (Montreal Convention Article 17(3)). You can claim your proven loss up to 1,519 SDR.
M
- Marketing carrier
-
The airline whose flight number is on your ticket in a codeshare. It is not necessarily the airline you claim from: EU261 and UK261 put the duty on the operating carrier.
- MCOL (Money Claim Online)
-
The online service for starting a County Court money claim in England and Wales. Flight compensation claims are normally allocated to the small claims track, where each side usually bears its own legal costs.
- Medical emergency
-
A passenger falling seriously ill on board, which may force a diversion. It can be an extraordinary circumstance; illness of the airline's own crew generally is not.
More: Medical emergencies
- Missed connection
-
Missing an onward flight because the first flight was late. If both flights were on one booking, you can claim compensation if you reach your final destination 3 hours or more late; separately booked self-transfer flights are assessed separately.
- Montreal Convention
-
The 1999 international treaty on airline liability for passenger delay, baggage and injury. It compensates proven loss up to set limits – since 28 December 2024, 1,519 SDR for baggage and 6,303 SDR for delay – with a 2-year court time limit. It is separate from EU261/UK261 fixed compensation, and you can use both.
More: Montreal Convention
N
- National enforcement body (NEB)
-
The authority each EU country designates to enforce EU261 (Article 16). Passengers can complain to it; in some countries it can order the airline to pay (LOT, C-597/20). In the UK the equivalent is the CAA.
- Notice period (14 days)
-
How far in advance you were told of a cancellation. Compensation is not due if you were told at least 14 days before departure, or later but offered a replacement close to your original times (EU261 Article 5(1)(c)).
O
- Operating carrier (also: operating air carrier)
-
The airline that performs, or intends to perform, the flight (EU261 Article 2(b)). It is the one responsible for compensation, care and refunds, including when it operates on behalf of another airline.
- Overbooking
-
Selling more seats than the aircraft has. If not enough passengers volunteer to give up their seats, the airline may deny boarding to others, who are then owed compensation immediately.
P
- Package holiday (also: package travel)
-
A holiday combining a flight with accommodation or other travel services sold together. You keep your EU261/UK261 rights against the airline, and may also have rights against the organiser under package travel law; a refund is claimed from the organiser, not the airline (HQ v Aegean, C-163/18).
- PACT
-
The CAA's Passenger Advice and Complaints Team. It reviews complaints about airlines that are not in an approved ADR scheme and can press the airline, but it cannot impose a solution.
More: Complaining to the CAA
- Passenger with reduced mobility (PRM)
-
A passenger whose mobility is reduced by disability, age, illness or another cause. EU261 Article 11 requires airlines to give them, their companions and unaccompanied children priority and care as soon as possible when disruption occurs.
- PIR (Property Irregularity Report)
-
The report you fill in at the airport baggage desk when a bag is missing or damaged. It gives you a reference number for tracing the bag and is the starting point of a Montreal Convention baggage claim.
- Pre-action conduct
-
The steps courts in England and Wales expect before a claim is issued: setting out your claim in writing, giving the other side time to respond and considering ADR. Ignoring them can affect costs.
R
- Re-routing (also: rebooking)
-
Alternative transport to your final destination under comparable conditions, either at the earliest opportunity or at a later date of your choice (EU261 Article 8(1)(b)–(c)). If the airline re-routes you to another airport serving the same city, it must pay the transfer.
More: Flight refund rights
- Reduced compensation (50%)
-
The airline may halve the compensation if it re-routes you and you arrive no more than 2, 3 or 4 hours (by distance band) after the original arrival time (EU261 Article 7(2)). Under UK261, the CAA explains that a 3–4 hour delay on a flight over 3,500 km gives £260 instead of £520.
- Refund
-
Repayment of the ticket price for the parts not flown (and parts flown if the trip no longer serves its purpose), due within seven days (EU261 Article 8(1)(a)). You can choose it instead of re-routing after a cancellation, denied boarding or a delay of 5 hours or more.
More: Flight refund rights
- Right of redress
-
The airline's right to recover what it paid you from whoever caused the problem, such as a tour operator or other third party (EU261 Article 13). It does not delay or reduce your claim.
S
- Scheduled time
-
The departure or arrival time on your booking. Delay is measured against the scheduled arrival time; care thresholds against the scheduled departure time.
- SDR (Special Drawing Right)
-
An international unit of account created by the IMF, valued daily from a basket of five currencies. The Montreal Convention sets its limits in SDR; Brazil's ANAC rules and others also use it. On 10 November 2026, 1,519 SDR was about £1,534 or €1,837.
More: Montreal Convention
- Security incidents and unruly passengers
-
Security alerts, airport security failures or a disruptive passenger forcing a diversion. They can be extraordinary circumstances (LE v TAP, C-74/19, on an unruly passenger), but the airline must still prove the link and its reasonable measures.
- Self-transfer (also: separate tickets)
-
Connecting between flights you booked separately. Each flight is a separate contract, so a delay on the first flight that makes you miss the second gives no compensation for the second.
- SHY-YOLCU
-
Turkey's Regulation on the Rights of Passengers Travelling by Air (2011), modelled on EU261. Since 10 December 2024 it also gives €100–€600 (paid in Turkish lira) when technical or operational delays make you arrive 3 hours or more late.
- Simple procedure
-
The Scottish sheriff court procedure for money claims up to £5,000, designed to be used without a lawyer. It is the Scottish equivalent of the small claims track.
- Slot (also: ATC slot)
-
A take-off time allocated to a flight by air traffic flow management when capacity is restricted. A slot imposed by air traffic control can be extraordinary; a slot missed because of the airline's own late boarding, crew or technical delay is not.
- Small claims track
-
The County Court track in England and Wales for most claims up to £10,000. Court fees depend on the amount claimed, and each side generally pays its own legal costs, so most passengers act for themselves.
- Strike
-
Industrial action. Strikes by people outside the airline, such as air traffic controllers or airport staff, can be extraordinary; a strike by the airline's own staff generally is not (Krüsemann, C-195/17; Airhelp v SAS, C-28/20).
More: Strikes and compensation
- Sturgeon rule
-
The Court of Justice ruling (C-402/07 and C-432/07, 2009) that passengers reaching their final destination 3 hours or more late can claim the same fixed compensation as for a cancellation. UK261 wrote it into Article 6(3) in December 2023.
More: Case law library
T
- Tarmac delay
-
Waiting on board the aircraft on the ground. The current EU261 does not regulate it; from 23 October 2027 the reformed rules require the aircraft to return to a gate or let passengers disembark after 2 hours at an EU airport, subject to safety and security exceptions.
More: The EU261 reform
- Technical fault
-
A mechanical or technical problem with the aircraft. Ordinary technical problems are part of an airline's normal activity and do not excuse a delay (Wallentin-Hermann, C-549/07; van der Lans, C-257/14; Jet2.com v Huzar).
- Time bar (Montreal Convention)
-
The 2-year limit for court actions under Montreal Convention Article 35. It does not apply to EU261/UK261 fixed compensation (Dawson v Thomson Airways, [2014] EWCA Civ 845; UK261 Article 3(7)–(9)).
More: Montreal Convention
U
- UK air carrier
-
An airline holding an operating licence from the UK Civil Aviation Authority. It matters for flights into the UK and EU, which UK261 covers when a UK carrier operates them.
More: UK261 explained
- UK261
-
The informal name for Regulation (EC) No 261/2004 as it now applies in UK law, with compensation of £220, £350 or £520. It covers flights departing the UK on any airline, flights into the UK on a UK or EU airline, and flights into the EU on a UK airline.
More: UK261 explained
- Upgrade
-
Being moved to a higher class. If the airline does this, it cannot charge you any supplement (EU261 Article 10(1)).
V
- Volunteer
-
A passenger who agrees to give up a seat on an overbooked flight in exchange for benefits agreed with the airline. Volunteers get a refund or re-routing but not the fixed denied-boarding compensation (EU261 Article 4(1)).
- Voucher (also: travel credit)
-
A credit for future travel offered instead of money. Under EU261 and UK261 compensation and refunds are paid in cash, by bank transfer or cheque; vouchers only with your signed agreement (Article 7(3)).
W
- Wallentin-Hermann
-
The 2008 Court of Justice judgment (C-549/07) holding that a technical problem is not normally an extraordinary circumstance and setting out the two-part test for extraordinary circumstances.
More: Case law library
- Weather
-
Weather conditions incompatible with safe operation – fog, storms, snow, low visibility – can be extraordinary circumstances, but only for the delay they actually cause on your flight, and the airline must still show it took all reasonable measures.
Missing a term? Tell us. For the key numbers in one place – amounts, thresholds and time limits with their sources – see key facts.
General information, not legal advice; we are not lawyers. We are an independent guide and an affiliate partner of AirHelp – see our affiliate disclosure.
Sources
- Regulation (EC) No 261/2004 (official text) – EUR-Lex
- Regulation (EC) No 261/2004 – UK version (UK261) – legislation.gov.uk
- Regulation (EU) 2026/2202 amending Regulation (EC) No 261/2004 – EUR-Lex
- Interpretative Guidelines on Regulation (EC) No 261/2004 (C/2024/5687) – European Commission
- Convention for the Unification of Certain Rules for International Carriage by Air (Montreal, 28 May 1999) – EUR-Lex
- Regulation (EC) No 861/2007 establishing a European Small Claims Procedure – EUR-Lex
- Alternative dispute resolution – UK Civil Aviation Authority
- Limitation Act 1980, section 9 – legislation.gov.uk
- Jet2.com Ltd v Huzar [2014] EWCA Civ 791 – The National Archives
- Lipton and another v BA Cityflyer Ltd [2024] UKSC 24 – The National Archives
We check every rule against the sources above. Spotted an error? Tell us – see our editorial policy.