The airline has cancelled 876 short- and long-haul flights today.

It says the unio extended the 24-hour walkout until the end of 24 November "for incomprehensible reasons… before Wednesday's strike even begun".

It adds: "They are inflicting extensive damage on our company.".

Both sides have argued before court. But the unio says that two courts have ruled the walkout – which covers pay – is legal.

unio board member Jorg Handwerg blames management for the dispute's escalation. In spite of the court rulings, he states: "The employer's representatives were unable to propose improved offers."

Lufthansa says it wants to start mediation in the long-running labour dispute, which included previous arbitration efforts and covers a range of work and pension terms.

But earlier this year, the unio requested limiting talks to pay negotiations and that other topics be left aside for the time being.