Extraordinary circumstances: what really excuses an airline

Most refused flight compensation claims are refused with the same phrase. This guide sets out what the extraordinary circumstances defence really is, the two separate hurdles an airline has to clear before it can rely on it, which causes the courts have already decided are not extraordinary, which ones usually are, and what you still keep even when the defence succeeds. By the end you should be able to read a refusal letter and tell whether it is worth arguing with.

The defence has two parts, not one

Article 5(3) of Regulation 261/2004 releases an airline from paying compensation where the disruption was caused by extraordinary circumstances which could not have been avoided even if all reasonable measures had been taken. The same wording sits in both regimes: the EU text is on EUR-Lex, and the version assimilated into UK law is on legislation.gov.uk. Which of the two applies to you is covered in UK261 vs EU261.

Read carefully, that is two tests, and the airline has to pass both.

1. Was the event extraordinary? The settled formulation is that the event must not be inherent in the normal exercise of the carrier's activity, and must be beyond its actual control. Both limbs have to be satisfied.
2. Did the airline take all reasonable measures? Even a genuinely extraordinary event does not excuse the airline automatically. It must show it did what could reasonably be expected to avoid the consequences - rerouting, calling in a spare aircraft, moving crew around.

Because this is a defence rather than a condition of your claim, the burden of proving it sits with the airline. A refusal that gives you one sentence and no detail has not discharged anything, and an ADR body or a court can say so.

What the courts have said is not extraordinary

Technical faults

This is the big one, because it is the most common reason given. In Wallentin-Hermann, C-549/07, the Court of Justice held that technical problems coming to light during aircraft maintenance, or caused by a failure to maintain, are inherent in running an airline and are therefore not extraordinary. The point was pushed further in van der Lans, C-257/14, where a component failed unexpectedly, before the end of its expected life, and was discovered during maintenance. Still not extraordinary. Breakdowns are part of operating machines.

The case law leaves a narrow exception open for hidden manufacturing defects revealed by the manufacturer or a regulator, and for sabotage or terrorism. Airlines occasionally reach for it. Ask them to name the defect and the safety notice.

The airline's own staff

In Krusemann and Others, C-195/17, a wave of unannounced sick leave by cabin crew after a surprise restructuring announcement was held not to be extraordinary, because the restructuring was the airline's own management decision. In Airhelp v SAS, C-28/20, the Court went further and held that a strike lawfully called by the airline's own staff, following the proper notice procedures, is also not extraordinary. Industrial relations with your own workforce are part of the business.

Crew illness

The UK Supreme Court settled this point in Lipton v BA CityFlyer, [2024] UKSC 24, where a captain reported unfit to fly shortly before a flight from Milan and no replacement could be found. The Court held unanimously that a member of staff falling ill is not an extraordinary circumstance. The judgment and its documents are on the Supreme Court case page.

What usually does count

The right-hand column is doing a lot of work. Nothing in this table is automatic, because the second hurdle still applies. Peskova and Peska, C-315/15 is the clearest illustration: a bird strike is outside the airline's control, but the Court still required the carrier to show it had taken reasonable preventive and remedial measures, including not wasting time on inspections it was not obliged to carry out.

The reasonable measures hurdle

This is where a lot of otherwise valid defences fall apart. A thunderstorm that closes an airport for ninety minutes is extraordinary. A six-hour delay after that storm may not be excused in full if the airline had a spare aircraft available, could have bought you a seat on another carrier, or could have rearranged crew rosters and simply chose not to. The question is not whether the airline was inconvenienced but whether it took the steps a reasonably diligent carrier would have taken.

Knock-on delays and the rotation argument

Airlines often say that your evening flight was late because the same aircraft was caught in a storm that morning. That argument can succeed: an extraordinary circumstance on an earlier rotation can excuse a later flight. But the airline has to show the causal chain properly, flight by flight, and it still has to show it took reasonable measures to break the chain, such as swapping aircraft or rerouting passengers. A vague reference to "earlier weather in the network" is not evidence. Ask which flight, which aircraft registration, and what was done about it.

A worked example

Three passengers fly London to New York, a route comfortably over 3,500 km, so the UK261 amount is £520 each. The aircraft goes technical at the gate, a part is replaced, and the flight lands 5 hours 40 minutes late. The airline refuses, citing "an unforeseen technical issue affecting the aircraft".

On the facts as stated, that refusal is wrong. van der Lans, C-257/14 covers exactly this: a part failing sooner than expected is not extraordinary. The delay is over four hours, so the Article 7(2) half rate does not bite either - that only reduces the amount on flights over 3,500 km where the arrival delay is between three and four hours. The claim is therefore £520 each, £1,560 for the three of them. Had the same flight landed 3 hours 30 minutes late, the half rate would have applied and the figure would have been £260 each, £780 in total. The compensation checker does that arithmetic for you.

What to do with a refusal letter

Reply in writing, quote the reason the airline gave back to it, and name the authority. Something as short as "you have described a technical fault, which Wallentin-Hermann, C-549/07 confirms is not an extraordinary circumstance" is enough to move most claims. If the cause genuinely might be extraordinary, switch to the second hurdle and ask what reasonable measures were taken. Keep whatever the airline told you at the airport, because the wording used at the gate often differs from the wording used in the refusal; proving your claim covers how to capture that at the time. The rest of the process, including what to send and when, is in claiming it yourself, for free, and if the airline holds its position after eight weeks, take it to an approved ADR body or the CAA.

One last thing worth repeating, because it is the most under-claimed right in the whole regulation. Extraordinary circumstances remove the compensation and nothing else. You keep your right to meals, communication and a hotel while you wait, and you keep your refund or rerouting rights if the flight was cancelled. A genuine storm defence should still end with the airline paying for the night you spent near the airport.