Lufthansa has confirmed the departure of its CEO Christoph Franz in another dramatic turn of events for the airline. Franz told Chairman Wolfgang Mayrhuber on Monday that he will not be available for another term at the top of the airline. His current term ends next April.

Franz said in a statement that professional reasons are behind his decision. He is joining Swiss pharmaceutical group Roche as Chairman.

The decision hits the airline at the worst possible time as its restructuring program is not yet delivering full results. Franz has been the driving force behind the program and sources inside the company are already voicing concerns that the restructuring could lose momentum once Franz is gone.

Sources with knowledge of the situation say the board of directors is unlikely to name a successor in the coming days. If the body decides to name a permanent replacement, Carsten Spohr, head of the passenger airline division, is seen as favorite although there are some reservations because of his more conservative approach to the restructuring. Swiss CEO Harr Hohmeister has been discussed, too, but he lacks the necessary backing in the passenger division.

If Lufthansa goes for an interim CEO, who would serve for 2-3 years, Lufthansa Cargo CEO Karl-Ulrich Garnadt and LSG SkyChefs’ Walter Gehl could be selected. One source said a short term return of former CEO Wolfgang Mayrhuber also cannot be completely ruled out.