Garnadt has been at Lufthansa since 1979, recently heading the group's cargo arm and its German airlines division before taking on responsibility for Eurowings at board level this year.

Garnadt turns 60 in January and he said he was stepping down because Lufthansa has a rule that board members must leave when they reach that age.

"This rule of course applies to me too," he said in a statement posted by the airline on Twitter.

The departure comes as Eurowings expands rapidly, taking on planes from Air Berlin and integrating Brussels Airlines as part of plans to become Europe's third largest point-to-point carrier.

The news was first reported by German daily Handelsblatt.

(Reporting by Peter Maushagen; Writing by Victoria Bryan; Editing by Maria Sheahan)