A strike by ground staff at Frankfurt airport, Germany's main hub, caused the cancellation Wednesday of scores of flights. According to DPA, the work stoppage by check-in desk staff and security personnel halted some 80 flights, the airport said. Long queues built up at check-in desks. The airports in Munich, Nuremberg, Stuttgart, Hanover and Hamburg also reported delays. The main German carrier Lufthansa said it had cut 142 domestic flights but that it intended to maintain its intercontinental services. Verdi, Germany's second-largest union with 2.2 million members, has embarked on "warning strikes" across Germany over recent weeks in support of an 8-per-cent wage demand for 1.3 million public sector workers. The federal government and the local authorities have refused to budge from an offer of up to 5 per cent over two years. In Berlin, around 12,000 public transport workers began an all-out, unlimited strike, halting underground rail, tram and bus services. The city transport authorities said they were running an emergency bus service. The shutdown hit the international tourism fair opening Wednesday in the German capital. On Tuesday, the GDL train drivers union announced that it would from Monday call out its members, representing some three quarters of Germany's 20,000 train drivers, on an unlimited strike. German Transport Minister Wolfgang Tiefensee appealed to the GDL to hold off on strike action and return to talks with the state-owned rail company, Deutsche Bahn. The dispute has been running since March last year.