A "backlash from ground staff", according to the BBC:
"German pilots staging their second 24-hour walkout have been met with protests from colleagues angered by their pay demands.
About 500 ground staff demonstrated in Frankfurt airport at the Lufthansa pilots' strike, which they say puts their own positions at risk.
They shouted over the pilots' attempt to read a statement of their demands, which include a 24% pay increase.
"These exaggerated wage demands are endangering our jobs," said Hans-Josef Weilbecher, head of the workers' council for the technical, ground crew and mechanics staff.
A Lufthansa spokesman said that, by midday, about 500 flights had already been cancelled. The airline hoped to run 200 of its planned 1,100 flights.
People booked on domestic flights have been asked to take the train, where their tickets are being accepted. Newspaper adverts displaying an emergency timetable have forewarned travellers and prevented the situation in airports becoming chaotic.
While Lufthansa claimed more pilots from the Vereinigung Cockpit trade union had turned up for work than during last week's strike, the union claimed that the strike was holding, and that the number of members taking action had increased.
Last week's strike cost the company DM 50m ($22.5m).
The pilots say they will continue staging 24-hour stoppages every Thursday until their demands are met. Talks between management and the union broke down on Wednesday, despite Lufthansa reportedly making an improved pay offer. However, the pilots said on Wednesday that they were confident they would soon be able to end their strike action.
The German Trade Union Federation (DGB) has criticised their action complaining that they are trying to cut themselves the biggest possible slice of the cake.
Margret Moenig-Raane from the service industry union ver.di told the Berliner Zeitung newspaper the pilots were exploiting their central role in the running of the company for their own interests.
Pilots say they are just trying to bring their salaries in line with those of pilots at other companies."