Europe's largest airline Lufthansa is struggling to prepare for the worst service disruption in its history as a planned pilot strike is expected to ground about two-thirds of its flights.

Lufthansa's 4,500 pilots voted on Wednesday to strike from Monday to Thursday next week to press their demands for job security, pay rises and a management promise not to outsource operations to worse-paid subsidiaries.

As a consequence, about 1,200 of the 1,800 daily flights have been canceled in advance. Passengers can check the Internet for the skeleton timetable of about 600 flights the airline still wants to service from Monday to Thursday.

The strike, which is due to start at 00:00 a.m. local time on Monday, will also involve Lufthansa's budget unit German Wings and its cargo subsidiary, Lufthansa Cargo.

Lufthansa regional service is said to be not affected. Also code-share flights are expected to operate normally.

Lufthansa, which has estimated the direct costs of the walkout at 100 million euros, has described the pilot strike as disproportionate.

Company spokesman Andreas Bartels said that the company had contacted pilot representatives on Friday to put forward a constructive proposal, which was apparently turned down by the trade union.

However, both sides have not ruled out an 11th-hour deal over the weekend.