Eurowings has come under fire in Germany recently for delays and cancellations, partly caused by its rapid expansion as it tries to move into the gap left by Air Berlin.
"Thanks to the successive introduction of further planes, we again expect a reliable flight operation," Eurowings CEO Thorsten Dirks wrote in a message to customers.
However, like other carriers such as Ryanair and IAG group airline Vueling, Eurowings and also Lufthansa has also had to cancel flights due to air traffic control strikes and staff shortages and weather.
Lufthansa has also written to frequent flyers apologizing for the delays. The group's core brand has canceled around 2,800 flights so far this year, more than in the whole of last year.
(Reporting by Victoria Bryan; Editing by Christoph Steitz)