"The plan is to take the final decision on Sept. 25," a spokesman for Air Berlin told Reuters. The decision on the bidding process was initially expected to come on Sept. 21.

Air Berlin, Germany's second-biggest airline, is set to be carved up, most likely among several buyers, with binding offers due on Friday.

Lufthansa, is seen in pole position to acquire large parts of Air Berlin. The insolvent carrier's supervisory board is also due to meet on Sept. 25, sources have told Reuters.