Malaysia Airlines CEO Christoph Muller is stepping down in September due to “a change in his personal circumstances”. The surprise announcement comes less than one year into Muller’s three-year contract. Muller was brought in to turn around the struggling carrier in the wake of the two tragic accidents — the disappearance of MH370 and the shooting down of MH117 — that hit the airline in 2014.

Peter Bellew, the current COO, will become executive director to facilitate the transition to the new CEO. Muller has committed to remaining on the board as non-executive director during this period.

Muller, the former head of Ireland’s Aer Lingus, had announced some drastic measures since taking over the top job in May 2015, including laying off one-third of the workforce, and recent results had shown the first tentative signs of recovery.

The airline is owned by the Malaysian government’s strategic investment fund, Khazanah Nasional. Khazanah said in a statement that a final decision on a new CEO would be taken by September 2016.

The airline union, NUFAM, said Muller’s decision was irresponsible and unacceptable, unless it was taken for health reasons. The union called on Muller “to stay on and finish the job”.