Employees of insolvent German airline Air Berlin protest before an Air Berlin news conference in Berlin, Germany September 25, 2017. REUTERS/Stefanie Loos

BERLIN (Reuters) - About 1,400 employees at Air Berlin AB1.DE are threatened by dismissal, union documents showed on Friday, with the insolvent carrier's entire ground staff due to get their notices of termination by the end of October.

Employees needed to maintain flight operations would be given notice by the end of February 2018, according to staff information seen by Reuters.

Other employees will probably be released from their duties, the information showed, without giving specific details. The dismissals also affect administrative staff.

Air Berlin declined to comment.

Earlier on Friday, the airline said it had extended the bid deadline for its maintenance division to allow potential buyers to adapt their offers depending on the outcome of talks for its other assets.

The carrier is in talks with Lufthansa LHAG.DE and easyJet EZJ.L on a carve-up of its assets such as aircraft, take-off and landing slots and crew. These talks are due to run until Oct. 12.

Air Berlin, which has around 8,000 employees, filed for insolvency in August after major shareholder Etihad said it would stop providing funding.