With security personnel at Germany's Hamburg and Cologne airports going on strike on Friday in a wage dispute, over 200 flights were canceled at both the airports, leaving thousands of air passengers stranded.

The strike - which did not affect Frankfurt and Munich airports, which are Germany's main hubs - was called by ver. di union, after the latest round of negotiations with the management came to an end last week without any acceptable offer.

The strike by the security workers at the two airports on Friday were the latest in the series of work stoppages that have been called by the ver. di union, which is the biggest services-sector union in Germany. In recent months, a number of daylong "warning strikes" have been staged by airport employees in the country to increase pressure in wage negotiations.

The wage dispute is essentially rooted in the fact that while the employers have offered the airport workers a 9 percent increase in wages, the ver. di union is seeking an approximately 30 percent wage hike for private security workers at airports.

The argument which the union has put forth to press for the wage increase that it is demanding is that the majority of airport workers who play a crucial role in trying to thwart terrorist attacks are underpaid.