German carrier Air Berlin has initiated legal action against the consortium that\'s currently building the German capital\'s new international airport. It seeks compensation for several delays in the opening date. Germany\'s second-largest carrier, Air Berlin, on Tuesday sued the consortium that is building Berlin\'s new international hub, the Berlin Brandenburg Airport. It said it had launched legal action over repeated delays in the airport\'s opening. \"We\'ve decided to make our claim for compensation through the courts,\" Air Berlin Chief Executive Hartmut Mehdorn said in a statement. Earlier this year, the construction consortium acknowledged it would miss yet another deadline for the planned opening date, which was June of this year. The airport is now expected to begin operations on October 27, 2013. Fewer clients Mehdorn said a legal battle had become unavoidable, because talks with the consortium on an out-of-court compensation settlement had failed. The CEO added Air Berlin had the obligation to protect itself against financial damage. The carrier gave no precise figure as to the scope of delay-related financial losses. It maintains that so far, additional costs are in the double digits in billions of euros (dollars). However, the final figure is dependent on how Air Berlin does this winter, as flights that were originally scheduled for Berlin Brandenburg will have to be routed through the existing Tegel airport. It is still unclear how well each airline\'s needs will be accommodated at Tegel this winter. Air Berlin, which is national carrier Lufthansa\'s biggest domestic rival, reported on Tuesday that passenger numbers dropped by 5.0 percent in October, with the carrier cutting over 6.0 percent of its overall capacity. In the first ten months of 2012, Air Berlin had 29.4 million passengers, down 5.1 percent from the levels seen in the same period last year.