David O’Brien, the Irish carrier’s chief commercial officer said the mistake had been “a certain blemish on an otherwise impeccable" record.

He told the Belfast Telegraph: “There was a screw-up, a management failure, whereby at a very specific level, 50% of the pilot leave was allocated in the last four months of the year, which doesn’t work.

"I think we have to work hard to regain customer confidence.”

Despite the problems, O’Brien maintained that Ryanair had compensated affected customers.

"It is logistically, very difficult, for an airline to go and find flights with another airline, for many people. But what we communicated was, you can have a refund, and in the case of those within the 14-day period, compensation... even if people had paid £9.99, they were still getting the compensation, which runs to hundreds of euros.

"And, other associated claims, such as re-routing, we will process as we receive them," he said.

Meanwhile, Ryanair announced that it had reinstated its Belfast-London service, with the route due to restart in March.