Dozens of Air Berlin flights have been cancelled after an unusually high number of its pilots called in sick.

The insolvent German airline grounded around 70 planes on Tuesday at hubs in Berlin, Dusseldorf, Hamburg and Cologne.

Air Berlin is Germany’s second-largest carrier. Last month it was forced to file for bankruptcy after its shareholder Etihad Airways withdrew funding following years of losses.

Bidders, including Lufthansa are reported to be waiting in the wings to buy parts of the failing airline.