Deutsche Lufthansa AG on Monday said it would cancel more than 1,700 flights for the following two days after its principal pilots union extended strike plans into a second week.

Lufthansa last week had to cancel thousands of flights after pilots grounded much of the German flag carrier’s operations over four days of strikes in a protracted dispute over employment terms. Each strike day cost the airline about €10 million ($10.6 million).

Lufthansa’s main pilots union, Vereinigung Cockpit, late Sunday said it had called on pilots for short-haul flights not to report to work on Tuesday. The union has also appealed to pilots flying mid-haul and the more lucrative long-haul services to join the walkout on Wednesday.

Lufthansa said about 816 of 3,000 flights would be canceled Tuesday, affecting around 82,000 passengers. The next day 890 flights will be grounded, with 98,000 passengers affected.

The airline, which said it was ready to resume talks with pilots, failed in its bid to get a German court to block the strike. The court said Lufthansa was appealing the decision. Similar motions last week failed.