Pilots at Lufthansa's budget airline, Germanwings, started a two-day strike on Thursday as German pilots' union Vereinigung Cockpit (VC) seeks to put pressure on management in a long-running row over pay and conditions.
The VC pilots staged 10 strikes last year, affecting hundreds of thousands of passengers and wiping up to 200 million euros (S$308 million) from 2014 operating profit at Lufthansa, which is trying to reduce costs to keep up with rivals.
The strike, affecting departures across Germany, is due to run until 2259 GMT on Friday.
Germanwings, which runs short-haul flights in Europe, said on Wednesday it expected to operate more than 60 per cent of the 900 flights normally scheduled over the strike period by using volunteer pilots or chartering planes from other airlines.
The row between pilots and management concerns early retirement benefits that Lufthansa wants to change for new starters.
The current scheme enables pilots to retire at 55 and still receive a portion of their pay until regular state pension payments kick in. Lufthansa wants to increase the earliest age at which its new pilots can retire to reflect increasing life expectancies and cut costs.
The pilots have also requested that management enter mediation talks on plans for the expansion of low-cost flights, which Lufthansa has refused.
The pilots oppose the way Lufthansa is pushing through the expansion, by using a small business that is not subject to the same collective labour agreements as pilots at its Lufthansa and Germanwings units.
Like rival Air France-KLM, Lufthansa wants to increase low-cost operations to win back market share lost to the likes of Ryanair and easyJet, which are expanding in its home market.