Air traffic control restrictions are one of the defences airlines invoke most frequently, and they occupy a complex position under EC261. Genuine ATC strikes and system failures are generally extraordinary circumstances. But the catch-all phrase "ATC restrictions" covers a broad spectrum of events, and many of them are part of the normal operational environment that airlines are expected to manage.
When ATC issues are genuinely extraordinary
ATC strikes are the clearest case. Air traffic controllers work for national aviation authorities, not for airlines, and when they walk off the job, airlines have no control over the situation and no influence over the dispute. A strike that closes airspace or dramatically reduces capacity is a textbook extraordinary circumstance.
Major, unforeseen ATC system failures — where the technical infrastructure that manages air traffic suffers an unexpected collapse — can also qualify. These are rare events (the most significant recent example was the UK NATS failure in August 2023. You can check Eurocontrol for historical ATC disruption data) that affect all airlines equally and are genuinely beyond any carrier's control.
When ATC issues are not extraordinary
Routine ATC congestion, flow control measures, and slot restrictions are a different matter entirely. European airspace is busy, and ATC regularly imposes speed and spacing restrictions, re-routing, and holding patterns to manage traffic. These are normal, predictable features of the aviation environment. Airlines build schedules and plan operations knowing that ATC restrictions will occur, and they should account for them.
Similarly, seasonal capacity constraints — such as increased ATC delays during summer holiday periods — are foreseeable. An airline that schedules tight connections during peak season and then blames ATC for the resulting missed connections is not describing an extraordinary event.
Demand specifics
If an airline cites "ATC restrictions," ask exactly what restriction was in place, which ATC centre imposed it, what times it applied, and how it specifically affected your flight. Vague references to air traffic control do not meet the burden of proof required for extraordinary circumstances.
How to verify ATC claims
Eurocontrol publishes network-wide delay data that can help you verify whether significant ATC disruptions occurred on your travel date. If the data shows normal operations while the airline claims ATC caused your delay, the defence becomes difficult to sustain. You can also check whether other flights at the same airport were operating normally. If they were, a flight-specific ATC claim is suspicious.
The reasonable measures test
Even when ATC genuinely caused an initial disruption, the airline must demonstrate that it took all reasonable measures to minimise the impact. Could it have rerouted the flight? Were earlier or later slots available? Did it rebook passengers promptly on alternative services? If the ATC issue lasted two hours but your delay was six, the airline needs to explain the gap.