German airline Lufthansa has estimated that strikes may have cost it almost €200m this year, after a further two walkouts by pilots last week forced the cancellation of thousands of flights.

Europe's largest airline in terms of revenue had put the cost of the previous eight pilot strikes this year at €160m, rising to €170m if strikes by other airport staff were included. 

"Our customers are infuriated and hugely disappointed," Kay Kratky, an executive at the group's Lufthansa German Airlines unit, said at an event in Frankfurt last night. 

The pilots are in dispute with management over an early retirement scheme that allows pilots to retire at the age of 55, which Lufthansa wants to alter for new starters and which the pilots want to keep. 

Pilots' union Vereinigung Cockpit has staged ten strikes this year, including two last week. It meets today to discuss a proposal by Lufthansa for mediation in the row.