Knock-On Delays: When an Earlier Flight Is the Excuse

In short: An airline can rely on an extraordinary circumstance that hit an earlier flight operated with the same aircraft – but only if there is a direct causal link to your delay, and only if it took all reasonable measures to stop the delay spreading (C-74/19, C-826/19). If the earlier delay had an ordinary cause – a technical fault, a slow turnaround, crew problems – it is not extraordinary at all, and you can claim €250–€600 (EU261) or £220–£520 (UK261) for a delay of 3 hours or more.

The rule: a direct causal link

A "knock-on" or "rotational" delay is a delay passed down from one flight to the next because the same aircraft (and often the same crew) operates them in sequence. Article 5(3) of Regulation (EC) No 261/2004 does not say whether an airline can rely on an event that affected an earlier flight. The Court of Justice answered that question in 2020: yes, with conditions.

The conditions come from two judgments and are repeated in the European Commission's 2024 guidelines:

The event on the earlier flight must itself be an extraordinary circumstance – external to the airline and beyond its control.
The earlier flight must have been operated by the airline with the same aircraft.
There must be a direct causal link between that event and the delay or cancellation of your flight. The national court decides this, looking in particular at how the airline operates the aircraft.
The airline must show it took all reasonable measures to avoid the knock-on delay.

Is it extraordinary? Knock-on scenarios

What delayed the earlier flight	Extraordinary for your flight?	Authority
Diversion to offload an unruly passenger, earlier flight of same aircraft, delay carried straight through	Can be	C-74/19 TAP
Storm reducing arrival capacity three flights back, delay carried straight through	Can be	C-826/19 Austrian Airlines
NATS failure, 28 August 2023, delays "directly caused" by its knock-on effects	Likely	CAA guidance, 30 August 2023
Technical fault, slow turnaround, late crew or catering on the earlier flight	No	Internal event (C-549/07 test)
Earlier extraordinary event, but the airline had time to swap aircraft or crew and did not	Usually no	Reasonable measures (C-74/19; C-294/10)
Earlier extraordinary event explains only part of your delay	Partly	Only that part is deducted (C-315/15)

The two leading cases

Transportes Aéreos Portugueses (C-74/19, 11 June 2020)

A passenger flew with TAP from Fortaleza to Oslo via Lisbon in August 2017. The aircraft due to fly the Fortaleza–Lisbon leg had, on its previous flight from Lisbon, diverted to Las Palmas to offload an unruly passenger. It reached Fortaleza late, the passenger missed the Oslo connection in Lisbon and arrived almost 24 hours late on TAP's next flight. The Court held that TAP could rely on the incident on the previous flight, provided there was a direct causal link – but also that re-routing the passenger on its own flight the next day was not a reasonable measure unless no earlier re-routing, on any airline, was available or it would have been an intolerable sacrifice.

Austrian Airlines (C-826/19, 22 April 2021)

A passenger booked Klagenfurt–Vienna–Berlin with Austrian Airlines on 21 May 2018. Stormy weather had reduced the arrival rate at the aircraft's turnaround three flights back in its rotation, and the delay carried through to the Vienna–Berlin flight. The Court held that an airline may rely on an extraordinary circumstance that affected a previous flight operated with the same aircraft at a turnaround three flights back, provided there is a direct causal link, which the national court must determine taking into account the way the airline operates the aircraft.

"Knock-on delays from earlier bad weather never count" – is that right?

Some UK consumer guidance lists a knock-on delay caused by bad weather on an earlier flight as not extraordinary, and says your own flight must be directly affected by the weather. Put that way, it is too broad. The Court of Justice has accepted in principle that weather three flights back can be relied on (C-826/19), and that an incident on the immediately preceding flight can be (C-74/19).

The consumer guidance does reflect what often happens in practice, though. A knock-on defence only works if the airline proves a direct chain and shows it did everything reasonable to stop the delay spreading. Many claims succeed precisely because the airline cannot do that – for example because it had hours to bring in a spare aircraft or crew, because the schedule left no reserve time, or because a separate internal problem joined the chain. The accurate summary is: an earlier flight's weather can be an excuse, but the airline has to prove the link and the reasonable measures, and often cannot.

Reasonable measures in a knock-on chain

Reserve time. The airline must build some reserve time into its schedule so that it can still operate a flight once an extraordinary event is over, though there is no fixed minimum for all airlines (C-294/10 Eglītis). A schedule with no slack at all makes a long knock-on delay more likely – and harder to defend.
Swapping aircraft or crew. Where a spare aircraft or standby crew was available, especially at the airline's base, the airline can be expected to use it. The Commission's guidelines note that airlines generally have more resources at their home base than at outstations.
Re-routing. If the delay grows long or the flight is cancelled, the airline must look for the earliest re-routing on its own or other airlines' flights (C-74/19).
Separating causes. If part of the delay arose from internal causes – a slow turnaround, a technical check, missing crew – only the extraordinary part is deducted (C-315/15). In the 2024 Touristic Aviation Services case (C-405/23), for example, the delay built up from three separate causes on the same day.

UK261: which rulings apply

The TAP judgment (C-74/19) was given in June 2020, before the end of the Brexit transition period, so it forms part of how UK courts read UK261. The Austrian Airlines judgment (C-826/19) came in April 2021 and does not bind UK courts, although they can have regard to it (Lipton v BA City Flyer [2021] EWCA Civ 454, para. 65). For the NATS failure of August 2023 the UK CAA said that delays and cancellations directly caused by its knock-on effects were likely to be extraordinary – the same "direct" test.

What the airline must prove

Which earlier flight was affected, by what extraordinary event, and when.
That the same aircraft then operated your flight, and how the delay passed from flight to flight – a timeline for each sector.
That nothing else (turnaround, crew, technical checks) added to the delay, or how much it added.
What it did to stop the delay spreading: reserve time, spare aircraft or crew, re-routing.

What you can do

Ask for the full chain in writing: the original event, the flight it affected, and the timeline through to your flight.
Check the aircraft's history. Flight-tracking sites show your aircraft's registration and every flight it flew that day. Look at whether the delay grew or shrank at each turnaround – if it grew, something other than the original event was at work.
Check the original event. If it was weather or an ATC restriction, see our guides to bad weather and air traffic control for how to check it.
Claim if the chain is broken or the airline did not take reasonable measures. If refused, escalate to the national enforcement body or ADR body of the country where the incident happened for EU, EEA and Swiss flights (see where to complain and our country guides, for example Germany, Spain, France or Italy), or ADR or the CAA for UK flights – see how to claim; the rulings are in our case law library.

Frequently asked questions

The airline says my flight was late because the aircraft arrived late from its previous flight. Can I claim?

Usually yes, unless the airline proves that the earlier flight was itself delayed by an extraordinary circumstance and that there is a direct causal link to your delay. A late incoming aircraft for ordinary reasons – a technical fault, a slow turnaround, a tight schedule – does not excuse the airline.

Bad weather hit the aircraft's first flight of the day. My evening flight arrived 4 hours late. Is that extraordinary?

It can be. In Austrian Airlines (C-826/19) the Court of Justice accepted that an airline may rely on weather that disrupted the aircraft three flights earlier, if there is a direct causal link. But the airline must show the delay carried straight through, and that it did what it reasonably could – reserve time, a spare aircraft or crew, re-routing – to stop it spreading. Many all-day knock-on delays fail on that second point.

How many flights back can the airline go?

The Court of Justice has accepted three flights back (C-826/19), but it did not set a fixed limit. The test is whether the link is direct, which the national court decides, taking into account how the airline operates the aircraft.

Can the airline rely on a problem with a different aircraft?

The two judgments on this point concern earlier flights operated by the airline with the same aircraft. If the airline is relying on disruption elsewhere in its network, ask it to explain exactly how that caused your delay; the burden of proof is on the airline.

Was the NATS failure in August 2023 an excuse for flights in the following days?

The UK CAA said delays and cancellations directly caused by the knock-on effects of the 28 August 2023 NATS failure were likely to be extraordinary circumstances. The word "directly" matters: a later delay with its own cause is assessed on its own facts. See air traffic control.

The crew ran out of hours because of the earlier delay. Does that count?

Only if the earlier delay was itself extraordinary and the airline could not reasonably have found replacement crew. If the earlier delay was internal, the whole chain is the airline's responsibility. See crew shortages.

General information, not legal advice. We are an independent guide, not lawyers and not AirHelp.

Sources

Regulation (EC) No 261/2004 – recitals 14 and 15 (as adopted) – legislation.gov.uk
Regulation (EC) No 261/2004 – Article 5 (as adopted) – legislation.gov.uk
C-74/19 Transportes Aéreos Portugueses, judgment of 11 June 2020 – Court of Justice of the EU
C-826/19 Austrian Airlines, judgment of 22 April 2021 – Court of Justice of the EU
C-294/10 Eglītis and Ratnieks, judgment of 12 May 2011 – Court of Justice of the EU
C-315/15 Pešková and Peška, judgment of 4 May 2017 – Court of Justice of the EU
C-549/07 Wallentin-Hermann, judgment of 22 December 2008 – Court of Justice of the EU
C-405/23 Touristic Aviation Services, judgment of 16 May 2024 – Court of Justice of the EU
Interpretative Guidelines on Regulation (EC) No 261/2004 (C/2024/5687), sections 5.3 and 5.4 – European Commission, Official Journal
Guidance to industry on the NATS flight planning failure, 30 August 2023 – UK Civil Aviation Authority
Lipton v BA City Flyer Ltd [2021] EWCA Civ 454 (status of later CJEU rulings, para. 65) – Court of Appeal (England and Wales)
Your flight compensation rights in extraordinary circumstances – Which?

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Knock-on delays: when the airline blames an earlier flight