Christoph Mueller is leaving Aer Lingus next year, the airline has announced.

In a stock exchange announcement this morning, Aer Lingus said it had "been agreed" between the company and Mr Mueller that he would step down as CEO and director in May 2015.

Mr Mueller was appointed as chief executive of the group in July 2009 and as an executive director in September of that year.

The airline's board said it would now commence a process to select and appoint a new CEO and executive director.

Aer Lingus Chairman Colm Barrington said the airline would be sorry to see Mr Mueller go and was grateful for his service over the past five years.

"Under Christoph’s strategic leadership, Aer Lingus has been transformed into a strong, consistently profitable airline with a clear strategic direction, a resilient business model as a value carrier and an improved cost base," he said.

Mr Mueller said he had "thoroughly enjoyed" his time at the airline, but felt it appropriate to announce his departure on the fifth anniversary of his appointment.

Minister for Transport, Tourism and Sport, Paschal Donohoe said: "Aer Lingus has performed very well under the stewardship of Mr Mueller and his management team. I'm sure he will be leaving the company next May in better shape than when he joined it and I wish him well for the future.

"This year the company is experiencing its fourth consecutive year of profitability, which is quite an achievement in a difficult trading environment."

Mr Mueller said he was willing to stay with the airline through May 2015 to help it work through the "significant challenges" it was continuing to address.

He said he would also be willing to facilitate the transition to his successor in the middle of next year.

"There remain a number of challenges for the company during the remainder of Mr Mueller's tenure and for his successor. Given the ample notice Mr Mueller has provided, the company now has the time to find a suitable replacement who will be up to these challenges," Mr Donohoe added.