German airline Lufthansa said Thursday it has cancelled more than 670 European flights owing to warning strikes by ground staff and other divisions within the group. Already on Wednesday, Lufthansa had said it would cancel most of its domestic and short-haul flights between 5:00 a.m. and midday (0400-1100 GMT) at the airports of Frankfurt, Munich, Duesseldorf, Berlin, Hamburg and Cologne as well as several other locations. The giant services sector union Verdi has called for walkouts to increase the pressure on management ahead of a second round of pay talks for around 33,000 ground staff and staff of the subsidiaries Lufthansa-Systems, Lufthansa Service Group (LSG), Lufthansa Technik and Lufthansa Cargo on Friday. Verdi is demanding a pay increase of 5.2 percent plus job guarantees. Lufthansa management had offered zero-wage increases for two years and longer working hours, an \"affront to all Lufthansa employees,\" the union said.