Air Berlin's Austrian associate carrier Niki is to become an affiliate member of the Oneworld alliance when the German airline joins in early 2012.
Niki, which is almost 50%-owned by Air Berlin, operates low-cost services from locations including Vienna.
Air Berlin has signed a memorandum of understanding with Oneworld regarding its membership of the group and says a formal alliance agreement will be "signed soon".
Its accession to Oneworld, which will come shortly before the opening of Berlin's new Brandenburg International Airport, will bring 75 more points to the alliance's network and take its destination count close to 900.
But Air Berlin is already planning to co-operate with Oneworld carriers American Airlines and Finnair through codeshares this year, and says bilateral agreements are intended with British Airways and Iberia.
"Joining a global alliance is the logical next step in Air Berlin's development," says chief executive Joachim Hunold.
"Becoming part of Oneworld would be one of the most significant departures so far for our airline, enabling us to offer our customers a truly global network served by partners who include some of the best and biggest airlines in the world."