Pilots at Deutsche Lufthansa AG extended their latest two-day stoppage, grounding long-haul flights in addition to domestic and European routes and stranding thousands of travelers. The strike, the ninth this year in a dispute over an early retirement scheme, has forced Germany's flagship airline to cancel close to half of all scheduled flights for Monday and Tuesday, affecting about 150,000 passengers. "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 pilots' union Vereinigung Cockpit (VC) board member Joerg Handwerg telling Reuters it could continue its walkouts into next year. 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. 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.