Aer Lingus CEO and director Christoph Mueller will step down from both posts in May 2015, the Irish flag-carrier announced Friday. He was appointed as CEO five years ago.

Mueller has been in charge through some turbulent times at Aer Lingus, notably the third attempt by low-cost Irish rival Ryanair to buy the airline. There has also been a long-running argument with staff over pension rights and industrial action.

His period at the helm has also seen the company become a member of Etihad Airways’ burgeoning equity alliance network.

Aer Lingus’s board will now start a selection process for Mueller’s replacement.

Chairman Colm Barrington said the company “will be very sorry to see Christoph leave. We are extremely grateful to him for his excellent service and positive contribution since 2009.

“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. Christoph has placed Aer Lingus in a position where we can look to the future with confidence and can continue to develop and grow the airline for the benefit of our customers, our employees and our shareholders.

“I am also particularly grateful to Christoph that in mutually agreeing a departure date that is some time away—in May 2015—Aer Lingus has sufficient time to both conduct a thorough process to select and appoint a new CEO to ensure that a comprehensive and seamless transition process is completed.”

Commenting on his experience at Aer Lingus, Mueller said he had “thoroughly enjoyed” his time in Dublin.

“The last five years has involved very hard work for the entire team at Aer Lingus and it is rewarding to see that the company is well positioned both strategically and financially. In that context and given it is the fifth anniversary of the date of my appointment, I feel it is the right time to hand over the reins.”