German airline Lufthansa cancelled around half of its scheduled flights on Friday as a 24-hour strike by cabin crew got under way, a company spokesman said.

Frankfurt airport, Lufthansa's main hub and Europe's third-busiest airport, was ‘most affected’ by the stoppages, the spokesman said.

But the head of the striking UFO labour union insisted that the situation in Frankfurt nevertheless remained ‘relatively calm’, as the carrier had obviously made better preparations this time round, which is the third separate day of walkouts since the industrial action began a week ago.

"On average, there are 1,800 Lufthansa flights during a normal day, around half of these flights will take place," said the Lufthansa spokesman.

"All German regions and all types of flights are affected," he said, including long-haul flights, which in the past strikes have been the least disturbed by the stoppages.

The strike began at midnight (2200 GMT), but its effect overnight was minimal as there were no overnight flights scheduled.

The company had been expecting to cancel 1,200 flights, or two-thirds, as a result of Friday's strike.

Already on Thursday, the carrier had cancelled around 50 flights ahead of the planned walkout by cabin crew at six major airports as the long-running dispute escalated.

And the Lufthansa spokesman said that around 13 flights were also expected to be cancelled on Saturday due to the knock-on effects of Friday's walkouts.

While unions and management had been in contact on Thursday, "there is nothing new to report" on the state of negotiations, the spokesman said.

The head of the UFO labour union, Nicoley Baublies, however, said he had sensed "clear signals that Lufthansa is willing to move."

"We'll see whether there can be talks this weekend," he said. "We'll do everything we can on our side. We have the impression that management are interested," he said.

Late Wednesday, the cabin staff's labour union, the Independent Flight Attendants' Organisation or UFO, said its members would stage a 24-hour stoppage Friday at the airports of Frankfurt, Berlin, Hamburg, Munich, Duesseldorf and Stuttgart in an escalation of their ongoing pay dispute.

Other much shorter walkouts of eight hours last week and earlier this week have grounded hundreds of flights and affected thousands of passengers.

The airline's CEO Christoph Franz, interviewed by ZDF television, acknowledged that he had "not anticipated a movement of this scale" but described it as "disproportionate."

According to its latest demands, the union -- which represents some two-thirds of Lufthansa's 18,000 cabin crew -- is seeking a five-percent pay increase backdated to April after three years of wage freezes.

It is also opposed to the use of temporary cabin crew on Lufthansa flights.

"We're prepared to go to mediation on the issue of pay hikes. But negotiations cannot include the use of temporary staff," a Lufthansa spokesman said.

The airline already faces headwinds because of rising fuel prices and fierce competition.

A 2009 strike by cabin crew cost Lufthansa tens of millions of euros.

In February, Frankfurt airport's apron control staff - traffic controllers who guide aircraft on the tarmac -- walked off the job over demands for higher pay.

According to Peter Oppitzhauser, an analyst at Credit Agricole Chevreux quoted by Dow Jones Newswires, the first two days of walkouts have already knocked 2.0 percent off Lufthansa's annual operating result, which is seen at around 500 million euros this year.