A spokeswoman for Germany's second-largest airline said on Wednesday morning that Berlin's Tegel Airport would see seven flights cancelled, while five flights would be nixed at Düsseldorf Airport.
The other flight cancellations would be spread over various airports. The spokeswoman also said it was possible for more flights to be cancelled later in the day on Wednesday.
Air Berlin had already announced on Tuesday that flight cancellations would take place on Wednesday, but did not give precise figures. The insolvent airline's chief executive Thomas Winkelmann wrote in an official letter in the evening that the company had received 149 sick notes from pilots for the following day.
airberlin still expects disruptions in air traffic tomorrow. Please check https://t.co/tkysHbzrIC before travelling to the airport.— airberlin (@airberlin) September 12, 2017
On Tuesday, some 200 Air Berlin employees had called in sick, more than 100 domestic and international flights were cancelled, and thousands of passengers were affected.
Winkelmann had said employees were "playing with fire" with their apparent protest action, which comes ahead of a Friday deadline for interested bidders to submit offers to take over parts of the company.
The day cost the company “several million euros,” Winkelmann had said in a statement.
"We are in the middle of final negotiations with potential investors. Stable operations are a prerequisite for the success of these negotiations. That's the only way we can secure as many jobs as possible."
Air Berlin filed for insolvency in mid-August, after its main shareholder, Gulf carrier Etihad, unexpectedly pulled the plug on its cash lifeline.
The airline had long struggled for survival, and booked losses amounting to €1.2 billion over the past two years.