Shareholders in Brussels Airlines must still agree to the deal, the statement said, adding that managers expect to complete the transaction by early 2017.
Lufthansa has owned 45 per cent of Brussels Airlines owner SN Airholding since 2009 and kept an option to buy the rest from around 30 remaining shareholders.
The companies did not reveal the price Lufthansa would pay for the remaining stake.
The Belgian carrier returned to profitability for the first time in years in 2015.
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A deadline for the German giant's final decision, originally set for June this year at the latest, was pushed back to September after Brussels airport was hit by twin suicide bombings on March 22.
Members of Lufthansa's supervisory board were also set to discuss a possible takeover of parts of deeply indebted Air Berlin, Germany's second-largest airline, German media reported yesterday.
A deal with Air Berlin could see 40 further aircraft added to the Eurowings roster -- currently at 90 jets.
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