The authority has taken the extraordinary step of issuing a 5pm deadline for the budget carrier to explain how it will re-route passengers on other airlines following its cancellation of 18,000 flights. The cancellations are caused by a pilot shortage and by Ryanair’s decision to fly 25 fewer aircraft this winter.

In a letter to Ryanair, the CAA says the airline must also include ‘a commitment to assist passengers who have chosen an option that was not suitable for them as a result of being misled by Ryanair’ and a promise ‘that Ryanair will reimburse any out of pocket expenses incurred by passengers as a result of the cancellations’.

The CAA says the airline must publish this information on its home page. The Authority’s crackdown comes after Ryanair said it would not re-route passengers on cancelled flights but would instead only provide refunds, which is in contravention of the EU261 consumer protection laws.

Ryanair chief executive Michael O’Leary had earlier said that the carrier “could not afford” to reroute passengers on other airlines because their fares were too high. Ryanair made a post-tax profit of £1.1 billion in the year to the end of March.

A CAA spokesperson told TTG: “We are currently in an enforcement period which has a minimum seven days.” This, he said, was launched on Wednesday and could be extended “if we think we are getting somewhere”.

The CAA has taken on the task of making the Irish carrier comply with the law because Irish Aviation Authority’s remit is focused mainly on safety and does not cover consumer protection.

The CAA has scheduled a conference call with Ryanair on Monday afternoon. The letter says this will ‘allow you to provide an explanation’ and adds: ‘We are especially interested to understand how Ryanair’s call centre staff applies your policy’.