“On Thursday, the group announced a record result,” said UFO union leader Joachim Vazquez Buerger.

“The cabin crew have to be able to benefit from this success, and the efforts made during the Coronavirus crisis must be rewarded.”

The strike will cover flights out of Frankfurt on Tuesday and from Munich on Wednesday, with Lufthansa’s subsidiary CityLine also affected. Lufthansa said later Saturday that around 100,000 travellers would be hit by the stoppages.

“We deeply regret coming to this point and ask passengers… to excuse us for the coming inconveniences,” he said.

On Thursday, Lufthansa reported that 2023 profits doubled on booming demand, with a net profit of €1.67 billion ($1.82 billion), substantially higher than a figure of €791 million in 2022. That marked a second straight year of profits for the group — whose carriers include Lufthansa, Eurowings, Austrian, Swiss and Brussels Airlines — after two years of losses due to the pandemic shutdowns.

The company also took the opportunity to warn about the “damaging” impact of a wave of industrial action at the start of this year. But employee representatives say salaries have not kept pace with the earnings, even as inflation has eroded their spending power, leading to a series of strikes since the beginning of this year.

The latest walkout began last Thursday, with Lufthansa ground staff staging a nationwide two-day strike after a previous walkout in February.

“After 15 rounds of talks without an agreement, we must assume that management wants the situation to worsen, at passengers’ expense,” the UFO’s negotiator Harry Jaeger said late Saturday.

Lufthansa has said it made “a very good offer that notably includes pay increases of at least 10 percent”.

It has proposed a bonus of €3,000 ($3,280) for cabin crew members and a pay increase of six percent in August, followed by a 3.25 percent increase a year later.