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What the defence actually is
Article 5(3) lets an airline escape paying compensation if the disruption was caused by extraordinary circumstances which could not have been avoided even if all reasonable measures had been taken. Two halves, and airlines usually argue only the first. Even a genuinely extraordinary cause does not help them if they could have reasonably worked around it.
The burden of proof is entirely theirs. You do not have to disprove anything. If they will not say what the cause was, they have not met it.
Excuses that generally do work
- Weather severe enough to stop the flight. Genuine, but check the date. If other aircraft were operating normally out of the same airport within the hour, ask them to explain that.
- Air traffic control restrictions and strikes by ATC staff. Outside the airline's control.
- Airport closures, security alerts and political instability.
- Bird strikes. Settled by the Court of Justice: extraordinary. But the airline still has to show it did not drag out the inspection unnecessarily.
- A passenger being disruptive or taken ill.
Excuses that generally do not
- Technical faults. This is the big one. The Court of Justice held in Wallentin-Hermann that a technical problem found in maintenance or revealed by it is inherent in running an airline, and not extraordinary. Later cases narrowed it further. If your refusal letter says "technical issue", you are probably owed the money.
- A strike by the airline's own staff. The Court of Justice has treated industrial action by a carrier's own crew as part of the normal exercise of its activity. Airlines keep arguing this one and keep losing it.
- Crew shortages, crew out of hours, rostering failures. Theirs to manage.
- "Knock-on delay from an earlier rotation." Only helps them if the original cause was extraordinary and they could not reasonably have recovered the schedule. Ask what the first cause was.
- Overbooking. Never a defence. It is a commercial choice.
The reply that moves things
When you get a bare assertion, send this:
You have declined my claim on the basis of extraordinary circumstances. The burden of establishing that defence rests with you under Article 5(3). Please provide the specific cause of the delay, the evidence supporting it, and details of the reasonable measures you took to avoid the disruption. Absent that information I do not accept that the defence is made out, and I will proceed on the basis that compensation is due.
A meaningful share of refusals do not survive that email, because the airline cannot produce the detail without either conceding the cause was ordinary or putting a technical fault in writing.
A cause can be extraordinary and still cost them
Even when the defence holds, the duty of care under Article 9 does not go away. A genuine weather cancellation still obliges the airline to feed you, accommodate you overnight with transport to the hotel, and either refund you or get you there. Those are separate rights and they are not capped by the compensation bands. Keep the receipts and claim them even when compensation itself is off the table.
Work out your own figure
Four regimes checked at once, no sign-up, and it shows you the article the number comes from.