Regulation (EC) No 261/2004 sets minimum rights for passengers when flights are delayed, cancelled or when boarding is denied. Passengers may be entitled to fixed compensation depending on flight distance and delay, but Article 5(3) creates an exception: carriers are not liable if they can prove that a cancellation or long delay was caused by extraordinary circumstances that could not have been avoided even if all reasonable measures had been taken. The European Court of Justice (CJEU) has built a body of case law defining these circumstances, balancing passenger protection with fairness to airlines.

The CJEU has clarified that two cumulative conditions must be met for an event to be an extraordinary circumstance:

• Not inherent in normal operations – the event must stem from causes that are not part of the airline’s usual activities or maintenance. Routine technical problems are generally inherent.
• Beyond the carrier’s actual control – the event must arise from outside the carrier’s sphere of control, such as acts of third parties, natural phenomena or hidden defects.

If both conditions are satisfied and the carrier can show it took all reasonable measures, compensation may not be due.

Routine maintenance issues

In Wallentin-Hermann v. Alitalia (C-549/07) the Court found that technical problems discovered during maintenance or caused by lack of maintenance are not extraordinary. The functioning of an aircraft inevitably gives rise to technical problems and carriers are expected to anticipate and manage them. Similarly, in van der Lans v. KLM (C-257/14) the Court held that the premature malfunction of components, even when unexpected, remains intrinsically linked to the aircraft’s operating system; such failures are considered routine and within the airline’s control. Only systemic defects affecting an entire fleet might qualify.

Failure of “on-condition” parts (2020 – C-832/18)

An “on-condition” part is replaced only when it becomes defective. In A and Others v. Finnair Oyj (C-832/18), the CJEU ruled that the failure of such a part is, in principle, part of normal aircraft operation and cannot justify non-payment of compensation. The Court held that a carrier may not rely on extraordinary circumstances arising from failure of an on-condition part unless the failure is not inherent in normal operations and outside its control. Because the failure is intrinsically linked to the aircraft’s operating system, it is normally not an extraordinary event.

Hidden design defects (2024 – C-385/23)

In Matkustaja A v Finnair Oyj (C-385/23), decided on 13 June 2024, the Court examined a flight cancelled when a new aircraft’s fuel-gauge failed. The defect was the first known failure of that component, and later investigations revealed a latent design flaw affecting all aircraft of the same model. The CJEU reiterated that technical failures are generally inherent in an airline’s activity but accepted that hidden manufacturing or design defects may constitute extraordinary circumstances if:

• The manufacturer or a competent authority confirms that the failure was unexpected and unprecedented and affects all aircraft of the same type;
• The defect impinges on flight safety, giving the carrier no reasonable opportunity to prevent or mitigate the failure.

Where these criteria are met, the event is considered external to the airline’s control and not inherent in its normal activity, allowing the carrier to avoid compensation. This ruling is significant because it provides a clearer definition of hidden defects and shows that the extraordinary-circumstances defence can apply to design faults beyond the carrier’s control.

External events and other examples

The Court distinguishes between internal events, which stem from the airline’s own operations, and external events, which involve third parties or natural phenomena. Only external events may qualify as extraordinary circumstances. Key examples include:

• Wildcat strikes: strikes organised by an airline’s own staff in response to restructuring or labour disputes are not extraordinary; airlines remain liable for compensation. Conversely, strikes by air-traffic controllers or airport staff may qualify because they originate outside the carrier.
• Bird collisions: a bird strike is considered an extraordinary circumstance. However, the carrier cannot justify further delay by conducting a second check once an authorised expert has found the aircraft airworthy.
• Collisions with airport equipment: damage caused by the airport’s mobile stairs colliding with an aircraft is not extraordinary because ground-handling services form part of the airline’s normal operations.
• Foreign objects on runways: damage to tyres from debris or the closure of a runway due to spilled petrol from another aircraft are external events and can constitute extraordinary circumstances.
• Unruly passengers: diverting a flight to disembark a disruptive passenger may be an extraordinary circumstance unless the airline contributed to the situation or failed to act on warning signs.
• Natural disasters: volcanic eruptions, such as the Eyjafjallajökull eruption that led to airspace closures, are extraordinary but do not remove the carrier’s obligation to provide care under Articles 5(1)(b) and 9.

The Court has also clarified that when an extraordinary circumstance occurs on a previous flight using the same aircraft, the carrier can rely on that event only if there is a direct causal link to the subsequent delay.

Even when an extraordinary circumstance exists, carriers must demonstrate that they took all reasonable measures to avoid or mitigate the delay. The Court has explained that airlines must plan flights with a reasonable reserve time to deal with unexpected disruptions but are not required to make intolerable sacrifices. If a carrier fails to deploy available resources (staff or equipment), it may still be liable for compensation.

Importantly, extraordinary circumstances do not remove the airline’s duty to provide care and assistance, such as meals, accommodation and re-routing; they only affect the payment of monetary compensation. Passengers should therefore still receive support when delays occur due to exceptional events.

The CJEU’s jurisprudence shows an evolving but balanced approach to extraordinary circumstances under Regulation 261/2004.

Routine technical issues and maintenance-related failures generally remain within the airline’s control and do not excuse non-payment of compensation. However, the Court recognises that certain hidden manufacturing or design defects, confirmed by manufacturers or authorities, can be truly extraordinary, as the Finnair judgments illustrate. External events such as bird strikes, debris on runways, volcanic eruptions or third-party strikes may also justify an exemption, whereas internal strikes or operational mishaps do not.

For airlines, these decisions underscore the importance of robust maintenance systems, contingency planning and clear documentation to demonstrate reasonable measures. For passengers, they provide guidance on when compensation is likely or when an exemption may apply. Overall, the Court’s case law seeks to balance high levels of passenger protection with fairness to carriers by insisting that only events truly outside an airline’s sphere of control absolve it from paying compensation.

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