German airline Lufthansa canceled hundreds of flights Thursday at its budget unit Eurowings, affecting some 40,000 passengers, because of a strike by cabin crew.

The airline said that about 400 flights were canceled, including most connections inside Germany.

Many of its European flights also were canceled but long-distance flights and those from Frankfurt and Munich weren’t affected.

The UFO union called the 24-hour strike starting at midnight after failing earlier this week to reach an agreement with management on various contractual issues and on conducting arbitration proceedings. Members are seeking concessions on issues including pay, working conditions and pensions.

Senior UFO official Nicoley Baublies stepped up the pressure on Thursday, telling news agency dpa that the union plans to call members out on strike on two days next week as well. He didn’t specify which days.

Eurowings also operates flights under the Germanwings brand. The airline said customers should check its website to see whether their flight is affected.

Lufthansa is trying to cut costs amid rising competition from Gulf state airlines and European budget carriers. The expanding Eurowings operation is an important element in its strategy.

(AP)