The deal has sparked controversy in the European aviation sector, with the German government facing accusations it helped steer the process under a plan to build the Frankfurt- based carrier into an all-conquering juggernaut.
Lufthansa will take over Air Berlin's Austrian subsidiary Niki, German subsidiary LGW and 20 further aircraft, guaranteeing all jobs at the two smaller firms, Air Berlin said in a statement.
The deal includes 81 of Air Berlin's 144 aircraft and 3,000 of its 8,500 staff, Lufthansa chief executive Carsten Spohr said in Berlin, hailing it as a "great day" for his company.
Spohr has suggested Easyjet is interested in up to 30 aircraft.
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Lufthansa has yet to say how much it will pay under the deal, but Spohr told newspaper Rheinische Post today that the group would invest 1.5 billion euros (USD 1.8 billion) in its low-cost subsidiary Eurowings following the takeover.
He added that 80 planes was the largest addition to Lufthansa's fleet that competition authorities would accept.
"We will only be able to breathe when the Commission has finally confirmed the transaction," Air Berlin boss Thomas Winkelmann said in the company's statement.
Many internal German routes will in future only offer a choice between Lufthansa and Eurowings.
But Spohr told business daily Handelsblatt today that "we expect the competition authorities to examine the takeover at least from the point of view of European competition, not limit it to the German market alone."
While the authorities investigate, Air Berlin will operate flights as a subcontractor, as insolvency rules forbid it from flying on its own account after October 28.
Its aircraft have been kept aloft by a 150-million-euro (USD 178 million) emergency loan from the German government while details of the breakup were worked out.
German and international investors and competitors lined up, with an eye not only on Air Berlin's aircraft but also coveted takeoff and landing slots at crowded airports.
In the race for exclusive talks, Lufthansa and Easyjet reportedly beat out IAG -- owner of Iberia and British Airways -- and three bids of between 500 million and 600 million euros apiece from private investors.
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