Employees of Frankfurt Airport's cargo and passenger controls went on strike early on Tuesday morning, with scores of flights canceled as a result.

The walkouts are part of a wage dispute between the Verdi trade union and the Federal Association of Aviation Security Companies.

The union is negotiating for a new agreement for some 25,000 security staff nationwide, with demands that include an increase in the hourly wage rate of at least €1 ($1.10).

How bad is the disruption?

According to Frankfurt Airport, 130 of 818 flights planned for Tuesday were canceled. Originally, some 71,000 passengers had been expected to be at the airport that day.

Only passengers with layovers were allowed to pass through security checks there, and the airport's operators advised people against traveling to board flights at Germany's biggest aviation hub.

Airport operator Fraport had called on all travelers hoping to board in Frankfurt not to travel to the airport.

There were also walkouts by employees at Hamburg, Stuttgart and Karlsruhe/Baden-Baden airports. Staff at Munich airport — Germany's second largest —   have been on strike since Monday afternoon.

Other airports — Berlin, Düsseldorf, and Hannover — canceled dozens of flights because of walkouts on Monday.

There have been three rounds of negotiations so far, which have failed to produce a result. The sides are planning to meet for further negotiations in Berlin on Wednesday and Thursday.

rc/wd (dpa, AP)