Airport security personnel went on strike fat the airports in Cologne, Düsseldorf and Stuttgart.
Germany"s largest trade union, announced the strike on Wednesday. Nearly 500 flights are postponed.
The union is currently in a wage dispute with the BDLS, an organization representing Germany"s airport security companies.
On Monday, security workers carried out a four-hour strike at Berlin"s Tegel and Schönefeld airports, causing around 80 flights to be delayed.