Over 100 national and worldwide flights were to be grounded, affecting schedules at major German airports including in Berlin, Dusseldorf and Munich, reports Efe news.
"We are now conducting final talks with potential investors".
Air Berlin, Germany's second-largest airline, filed for bankruptcy protection last month after shareholder Etihad Airways withdrew funding following years of losses. "A stable operation is mandatory for these negotiations to succeed".
The ailing carrier was forced to cancel more than 100 flights, including transatlantic connections, as a result of the sick notices, causing chaos at several German airports.
A deadline to submit bids to acquire Air Berlin or parts of it has been set for 15 September.
Germany's giant services sector union Verdi on Tuesday expressed solidarity with the absent pilots and warned that more workers could call in sick. That is crucial in order to bring talks with investors to a successful conclusion.
Lufthansa's low-priced division Eurowings - which is wet-leasing Airbus A320-family jets from Air Berlin - has been affected.
Board member Christine Behle states: "All talks about insolvent Air Berlin revolve around economical interests, but not the jobs of more than 8,000 employees".
Intro wants "Air Berlin as a whole" rather than buying up chunks, Woehrl emphasised, urging other potential buyers nosing around the airline like Lufthansa, Condor, TUI, Germania and Austrian former Formula One driver Niki Lauda to join his offer.
Air Berlin continues to fly during the preliminary insolvency proceedings due to an EU-approved loan of EUR€150 million (USD$179 million) agreed at the beginning of September.