Pilots at Deutsche Lufthansa said they would strike again on Thursday on long-haul and cargo flights, after a two-day stoppage on Monday and Tuesday stranded thousands of travellers.

The union said in a statement that short and medium-haul flights and those of budget carrier Germanwings would not be affected by the action on Thursday.

The strike, the ninth this year in a dispute over an early retirement scheme, forced Germany's flagship airline to cancel close to half of all scheduled flights for Monday and Tuesday, affecting about 150,000 passengers.

Lufthansa is trying to squeeze its cost base to compete with low-cost carriers like Ryanair Plc and easyJet Plc , as well as Gulf airlines, but has met resistance from workers.

Pilots' union Vereinigung Cockpit (VC), representing about 5,400 Lufthansa pilots, is fighting to retain a scheme allowing pilots to retire at 55 and still receive up to 60 percent of their pay before regular pension payments start at 65.

"We cannot keep doing this for the next year or two, we need to sit down and find a solution," Lufthansa spokeswoman Barbara Schaedler told Reuters TV.

Pilots however showed no sign of backing down, with VC board member Joerg Handwerg telling Reuters it could continue its walkouts into next year.

Lufthansa has said it would not accept a demand that new pilots, as well as those already with the company, should be able to retire at 55.

In the meantime the stoppage is causing frustration among customers. "We only found out about the strike in Germany just before departing Chicago," said Paula Herman, 47, part of a group travelling from the United States to Israel.

"(The pilots) are totally messing up other people's plans. Our trip to Israel is once-in-a-lifetime," she told Reuters at Germany's busiest airport, Frankfurt.

Under European Union law, pilots may legally fly until they are 65 but many airlines offer early retirement options.

According to VC, pilots at British Airways, part of International Consolidated Airlines Group SA, can take early retirement from 55, and pilots at KLM, part of Air France KLM SA, can stop work at 56.

The industrial action has already wiped 160 million euros ($200 million) off Lufthansa's operating profit and the airline lowered its profit guidance for 2015 for a second time in October, increasing pressure to find an end to the dispute.

Lufthansa said it would be able to operate all scheduled cargo flights on Tuesday despite the strike. – Reuters