In late April, Germany's biggest airline said its net loss widened nine-fold to 342 million euros ($385 million) in the first three months of the year, hurt by rising fuel costs and excess capacity in Europe.

Asked about summer bookings, Carsten Spohr told Neue Zuercher Zeitung: "It is looking good, not just with regard to business travelers. That's why we've said that we'll be seeing better quarters compared with the first."

European airlines are battling overcapacity and high fuel costs, while uncertainty around Brexit has led some travelers to delay booking flights for their summer holidays.

(Reporting by Christoph Steitz, editing by Louise Heavens)