High Court Ruling Strengthens Legal Precedent on Airline Delays Due to ATC Slot Restrictions

A recent High Court ruling on March 3, 2025, has reinforced existing legal precedent regarding airline liability for delays caused by Air Traffic Control (ATC) slot restrictions. The court ruled in favor of the airline, finding that delays resulting from ATC-imposed slot limitations qualify as extraordinary circumstances, even when they cause knock-on delays in subsequent flights.

Key Aspects of the Decision

The case revolved around whether the airline was liable to compensate passengers for a delay exceeding three hours on a flight from Billund to Edinburgh. The claimant, CMC, argued that the airline had been aware of the initial delay 10 hours before departure and should have taken measures to mitigate its impact on later flights. However, the High Court ruled in favor of the airline, concluding that:

• ATC slot restrictions constitute extraordinary circumstances under EU Regulation 261/2004, regardless of whether the airline had prior knowledge of the initial delay.

• The airline had taken all reasonable measures to prevent or minimize the delay, thereby fulfilling its obligations under EU law.

The ruling builds upon previous case law and clarifies that delays caused by ATC decisions remain outside an airline’s control, even when they affect subsequent flights within a tightly connected schedule.

Case Details

The dispute stemmed from a flight that was significantly delayed due to ATC slot restrictions affecting earlier legs of the aircraft’s schedule. ATC Slot History reports showed that adverse weather conditions led to successive slot limitations, resulting in a cumulative delay of 3 hours and 25 minutes.

The claimant argued that the airline failed to take alternative measures being aware of the initial delay in advance. However, the High Court found that ATC slot restrictions -imposed independently by air traffic control - should not be attributed to the airline.

It was emphasized in the defense that an airline cannot assign its own ATC slots, as these are regulatory tools used by air traffic management authorities to control congestion and ensure flight safety.

In its defense, the airline referenced case C-826/19 of April 22, 2021, where the European Court of Justice ruled that an event classified as an extraordinary circumstance also applies to subsequent rotations if there is a direct causal link between the original extraordinary event and the delay of the later flight.

Furthermore, in accordance with case C-74/19, the airline argued that it had taken all reasonable measures to avoid or minimize the delay. It was emphasized that the airline's prior knowledge of a potential knock-on delay was irrelevant, as the decisive factor was whether, after passenger check-in, the airline could demonstrate that the flight was operated at the earliest given opportunity.

Legal Impact and Precedent

This ruling strengthens existing case law in favor of airlines, clarifying that ATC-related slot restrictions qualify as extraordinary circumstances, even when they create a chain reaction of delays.

The decision sets a precedent for future cases, offering clearer legal guidance for both airlines and claimants in disputes over flight compensation.

Going forward, this judgment is expected to influence how lower courts assess airline liability in similar cases, reinforcing the principle that delays stemming from ATC interventions remain beyond an airline’s direct control.

Attorney-at-law Henning Romme-Mølby, acted on behalf of the airline in the High Court.