Lufthansa flight attendants walked off the job for eight hours Friday at Frankfurt airport, Germany's biggest, causing the cancellation of more than 220 flights. Their union warned of more stoppages unless the airline gives in to its demands.

Lufthansa, Germany's largest airline, said it canceled more than 220 short- and medium-haul flights from and to Frankfurt, including routes across Europe and destinations including Tel Aviv, Tripoli and Beirut, after some 1,000 cabin crew went on strike. A small number of long-haul flights were canceled as well, among them services to and from New York, Boston, Atlanta, Philadelphia and Seattle.

The strike had a spill-over effect on other airlines after the airport, Europe's third-busiest, ran short of aircraft parking spots thanks to the grounded Lufthansa planes. It had to halt all Frankfurt-bound departures from other European cities for 40 minutes, airport spokesman Christopher Holschier said.

Thousands of stranded passengers crowded Frankfurt's main terminal building waiting for word on their flights. Lufthansa workers handed out water and juice to people stuck in long lines.

Airline spokesman Klaus Walther accused the UFO union of putting its demands "on the back of the customers" and urged it to return to the negotiation table.

The flight attendants stopped work at 5 a.m. (0300 GMT) and stayed on strike until 1 p.m. (1100 GMT) in what UFO union head Nicoley Baublies said on Bayerischer Rundfunk radio may just be the beginning if Lufthansa does not meet its demands. The union called the strike after 13 months of negotiations for higher pay and guarantees on conditions failed to produce an agreement.

"It depends on how Lufthansa responds now and how much they try to break the strike and put our people under pressure," Baublies said. He said the union would decide Friday whether to stage similar strikes again Saturday and whether to expand them to other airports.

"That's always possible and we will announce it with six hours' notice," he said.

UFO is seeking a 5 percent pay raise for the airline's more than 18,000 cabin crew workers. Lufthansa has said it is offering a 3.5 percent raise.

Other issues include the union's opposition to Lufthansa's demand that flight attendants assigned to Berlin's new airport, whose opening has been delayed, work more hours than elsewhere for the same pay. The two sides are also at odds over the possibility of Lufthansa transferring flight attendants to its partner budget airlines with cheaper contracts as part of a cost-saving program.

Lufthansa is trying to cut some €1.5 billion ($1.9 billion) from its costs by the end of 2014.


Christoph Noelting contributed to this report from Frankfurt