Air Berlin will stop considering offers to purchase the troubled German airline on September 15.
"Air Berlin will close the investor process quickly," a company spokesman said Tuesday.
Germany's second-largest commercial airline filed for insolvency two weeks ago after its main shareholder, Abu Dhabi-based Etihad Airways, withdrew financial aid for the loss-making carrier.
German flagship carrier Lufthansa has expressed an interest in buying a large share of assets in the bankrupt airline.
Air Berlin officials have said that they are also in talks with three other interested parties.
Britain's easyJet and German vacation airline Condor are also considered to be potential investors.
On Wednesday, a meeting is scheduled with German entrepreneur Hans Rudolf Woehrl, who is interested in purchasing the company as a whole.
