Air Berlin, Germany's number two airline, said Tuesday it will sue for damages over the renewed delay to the opening of Berlin's new main airport.
"We have decided to pursue our claims for compensation via the courts," said chief executive Hartmut Mehdorn.
"We have previously tried to find a solution that is acceptable for both sides via intensive negotiations with the airport. Unfortunately, we have not succeeded and so we now see filing a suit as the only way to defend our interests," Mehdorn said.
Air Berlin said it could not yet fully gauge the losses incurred by the delays, but so far they have run into the "double-digit millions" of euros (dollars).
The carrier complained that it has expanded its services to and from the German capital by an additional 230 weekly flights.
"These must be carried out at Tegel airport, where there is not sufficient infrastructure to cope," it argued.
Initially slated to open on June 3 this year and replace the city's current two hubs, Schoenefeld and Tegel, the Berlin-Brandenburg International Airport was delayed indefinitely in May after problems over fire safety.
The planned opening date is now October 27, 2013.
The scandal has dented the popularity of Berlin mayor Klaus Wowereit, accused of incompetence and underestimating construction problems.
The country's top two airlines, Lufthansa and Air Berlin, have expressed outrage over the repeated delays to the project, which is on the site of the current Schoenefeld Airport, in the southeast of the city.
Lufthansa said it has not yet decided whether to claim damages and declined to estimate the possible amount.
Berlin's airports are not the country's busiest, with Schoenefeld and Tegel combined welcoming around 24 million visitors a year -- less than half the 56 million passengers serviced at Frankfurt airport in western Germany.
But the new airport, to be named after former chancellor Willy Brandt once opened, is intended to accommodate the sharp rise in air traffic to the region seen since the fall of the Berlin Wall and German reunification.
It is due to service around 27 million passengers a year.
Berliners were already mourning the closure of Tegel, which is relatively close to the city centre and whose small, hexagonal main terminal is a 1960s relic that allows passengers to hop in or out of a taxi just outside their gate.