Germany's second-largest airline, Air Berlin, which declared bankruptcy last month after years of losses, was forced to cancel dozens of flights on Tuesday due to an unusually high number of pilots calling in sick. A decision on the fate of Air Berlin could come as quickly as September 21, three days before the German national election.
A wildcat walkout by Air Berlin pilots could "threaten the existence" of the under-fire carrier, its chief executive has said.
The company had to cancel more than 110 flights out of a planned 750 on Tuesday because of the walkout.
Departures information on Air Berlin's website showed flights cancelled from a range of German airports including Berlin Tegel, Duesseldorf, Hamburg and Cologne.
"We are now conducting final talks with potential investors".
AXEL SCHMIDT REUTERS Air Berlin had to cancel flights at Tegel airport in Berlin
"A stable operation is an essential precondition for successful negotiations", Mr Winkelmann said.
After losing the lifeline of regular cash infusions from Gulf carrier Etihad in June, Air Berlin filed for insolvency on August 15. "This is the only way we can protect as many jobs as possible".
Air Berlin has announced it will end long-haul flying, which many crew regard as the best option - it offers higher earnings and, for some, a better lifestyle. Germany's government has backed a €150 million ($179 million) bridging loan, and talks with potential investors are under way.
German service-sector union Verdi argues that it is "not at all surprising" that pilots have called in sick, given Air Berlin's current situation.More news: Philippe Coutinho trains with Liverpool ahead of Champions League opener