BERLIN, GERMANY - Lufthansa, the biggest German airline, faces a tumultuous strike during its busiest season after members of the German trade union Verdi voted to press demands for pay raises.

Ground personnel and flight crews would stop working on Sunday at midnight, the union said last week after workers it represented approved the action by an overwhelming majority of 90.7 per cent.

Lufthansa has said it is ready to pursue talks with union delegates who broke off negotiations, and an airline spokeswoman expressed 'incomprehension' at the announcement.

Verdi wants a 9.8 per cent pay raise over a year for around 50,000 workers, while Lufthansa has offered 6.7 per cent over 21 months.

Verdi negotiator Erhard Ott promised 'major disruptions' this week and urged passengers who were preparing to take summer holidays to show understanding for strikers' demands.

'We are aware that we are going to cause big problems for passengers,' Mr Ott said.

Lufthansa transports 150,000 people daily on average, and July is one of its busiest months.

The German association of travel agents DRV urged both sides to return to the negotiating table, saying a strike would hit 'uninvolved third parties in a disproportionate manner; it cannot be in the workers' interest to harm paying customers through massive flight cancellations, and ruining many peoples' vacations', the group added in a statement.

It was not immediately clear however how widespread the strike might be in initial stages, though Lufthansa's hubs in Frankfurt, Munich and Dusseldorf were among 11 airports that faced early disruptions.

Mr Ott said there would not be a blanket paralysis of German airports at the start of the action but that all would be affected at some point next week.

Lufthansa was working on a back-up plan with the German railway Deutsche Bahn, which said it was well prepared to handle extra demand.

Lufthansa boss Wolfgang Mayrhuber has insisted that the carrier 'cannot do any more' than its latest offer owing to 'extremely limited economic room to manoeuvre'.

But unions point to Lufthansa's operating profit last year of 1.38 billion euros (S$2.95 billion), a figure it expects to reach again in 2008, as proof the company can afford to meet workers' demands. - AFP