Lufthansa is facing a walkout on Friday after trade union UFO called on about 600 flight attendants in Frankfurt to stage a warning strike, the union said on Thursday.

The strike would last from 0515 GMT until 0815 GMT, during which time Lufthansa was scheduled to operate upwards of 70 flights out of its main hub, most of which are domestic and intra-European flights.

A spokesman for the airline said it was too soon to estimate the impact of the warning strike on its operations, noting Lufthansa had taken internal measures to minimize any effects as much as possible.

UFO earlier this month said it could launch warning strikes after a third round of wage talks for a total of 16,000 flight attendants failed. The union is calling for a wage and benefits rise of 15 percent for 12 months.

Lufthansa has increased its offer to a rise of up to 10 percent, from 9.1 percent. The package includes better work conditions and profit sharing.

The German airline called on UFO to return to the negotiating table and face up to "economic realities".

Last July, Lufthansa's passenger numbers were hurt as strikes by ground staff and cabin crew as well as walkouts by regional pilots forced the carrier to cut flights.

The wage agreement that ended that walkout adds about EUR100 million euros (USD$129.8 million) to costs every year, the company has said.

In addition, airlines have been hard hit by the escalating financial crisis, with passenger numbers dwindling. Lufthansa in October cut its 2008 operating profit goal to EUR1.1 billion, from a previous estimate of about EUR1.38 billion.