Regulation EC261 exempts airlines from paying compensation if the delay was caused by extraordinary circumstances that could not have been avoided even if all reasonable measures had been taken. The test has two parts: the event must be (1) extraordinary — outside normal airline operations — and (2) unavoidable even with all reasonable precautions. Both tests must be met.
1. Aircraft technical fault — almost always NOT extraordinary
Technical faults are the most commonly cited excuse and the most commonly overturned. The European Court of Justice ruled in Wallentin-Hermann (C-549/07, 2008) that technical problems are inherent to normal airline operations. Airlines are expected to maintain aircraft to airworthy standards — a fault is evidence of a maintenance failure, not an unforeseeable external event. German courts in particular consistently reject this defence.
Exception: A manufacturing defect concealed by the aircraft manufacturer and discovered unexpectedly — this could qualify as extraordinary. Hidden defects are treated differently from foreseeable maintenance issues.
2. Crew or staff shortage — NOT extraordinary
Airlines are responsible for ensuring adequate staffing. A pilot who calls in sick is a foreseeable operational risk — airlines build in redundancy for exactly this reason. If they don't have enough spare crew, that's a planning failure, not an extraordinary circumstance. Multiple UK and EU court decisions have confirmed this.
3. Late-arriving aircraft from a previous sector — NOT extraordinary
When an earlier flight delay causes your flight to delay because the aircraft hadn't arrived yet, airlines often cite the original disruption as extraordinary. Courts have ruled that rotational scheduling is entirely within the airline's control — they choose to schedule aircraft in tight rotations. The knock-on delay does not inherit the extraordinary status of any earlier event.
4. ATC (air traffic control) restrictions — CONTESTED
Genuine ATC capacity restrictions imposed by authorities can qualify as extraordinary. However, this defence is heavily abused. If the ATC restriction was foreseeable (e.g. a known scheduled ATC strike, or recurring slot pressure at a busy airport during summer), the airline may still be required to take all reasonable measures — including rerouting or rescheduling — and failure to do so voids the defence.
Important: Air France internal union strikes are NOT extraordinary (Krüsemann, ECJ 2018). DGAC (French ATC) strikes are contested. Always check which type of strike caused your disruption.
5. Bad weather — SOMETIMES extraordinary
Severe weather can qualify, but the bar is high. Routine fog, light snow, or wind within normal operational parameters does not qualify. The airline must show the weather was genuinely exceptional and that even with all reasonable measures, the flight could not operate safely. A 30-minute thunderstorm delay that stretches to 6 hours due to the airline's own subsequent scheduling failures is not continuously extraordinary.
6. Airline staff strike — depends on who's striking
This is the most legally nuanced area. A strike by the airline's own employees (cabin crew, pilots, ground staff) is NOT extraordinary — the ECJ ruled in Krüsemann (2018) that it is a 'normal exercise' of workers' rights within the airline's sphere. However, a strike by external parties — ATC controllers, security staff, ground handling agents employed by the airport — may qualify, provided the airline couldn't have avoided or mitigated it.
Pro tip
When an airline cites extraordinary circumstances to reject your claim, ask them specifically: (1) What was the cause? (2) What reasonable measures did you take? They must answer both — and courts are unimpressed by vague claims of weather or ATC without documentation.
The burden of proof lies with the airline. They must demonstrate both that the cause was extraordinary AND that they took all reasonable measures. You do not need to prove that circumstances were ordinary — they need to prove they were extraordinary.