Two days of strikes by aviation security staff at six German airports have led to a total of 662 cancelled flights affecting some 100,000 passengers, the ADV airport association said on Friday. Passengers at the Hanover, Dortmund, Dresden, Leipzig, Karlsruhe/Baden-Baden airports and Weeze airport in western Germany were affected after trade union verdi called for strikes by aviation security staff. The first employees went on strike in Hanover late on Thursday. Verdi is trying to increase pressure on the employers ahead of the next round of negotiations on 20 March. Unions are currently hittin…