The budget airline had tried to avoid paying compensation to affected customers by claiming that the industrial action by its staff amounted to ‘extraordinary circumstances’.

The ‘extraordinary circumstances’ clause can be used by airlines to not pay compensation due to customers under European Union rules. It often applies during adverse weather conditions.

Ryanair was forced to cancel hundreds of flights a day over the summer of 2018 following a series of walk outs by pilots and crew members across Europe. It then rejected claims for compensation by affected passengers, prompting the Civil Aviation Authority (CAA) to take enforcement action against the airline.

Ryanair was found in breach of the rules by the High Court in April but appealed against the decision. That appeal has now been dismissed by the Court of Appeal.

Lord Justice Newey said the strikes did not constitute “extraordinary circumstances, as they related to Ryanair’s employment conditions”.

At the time of the disruption, passengers whose short-haul flights to or from UK airports were cancelled within 14 days of the departure date were entitled to up to €250 (£208) compensation based on the timings of alternative flights offered.

Paul Smith, director at the UK Civil Aviation Authority, said: “Ryanair has refused to pay compensation to passengers affected by industrial action taken by its pilots in 2018. We believed that these passengers were in fact protected by law and that Ryanair could not claim its delayed and cancelled flights were ‘extraordinary circumstances’. The Court of Appeal has today upheld the High Court’s agreement with our interpretation of the law.

“We are committed to protecting the rights of air passengers and are determined to ensure all airlines comply with their legal obligations. We would like to advise consumers that Ryanair may seek to appeal this judgment to the Supreme Court. Affected customers should therefore await further information before pursuing their claims.

“Given consumers have been waiting for clarity on this subject since 2018, this process reinforces the need to modernise our powers. In this respect, we welcome the government’s recent consultation on strengthening airline passenger rights.”

Rory Boland, editor of Which? Travel, said: “Ryanair has tried every trick in the book over more than three years to wriggle out of its legal obligations and it is no surprise to see the court has ruled against it. The company must now finally do the right thing and pay its passengers the compensation they are owed, as well as improving its customer service and complaints handling procedures going forward.

“This episode underlines why reform of the travel sector is so badly needed. The government must press ahead with plans to give the CAA stronger powers – including the ability to fine airlines like Ryanair when they consistently flout the rules.”