A strike by about 4,000 Lufthansa cabin and ground staff over pay caused only minor disruption in Germany on Monday but a number of European flights were likely be cancelled on Tuesday, the airline said.
Maintenance work on nine aircraft, six in Frankfurt and three in Munich, was not performed as scheduled and they would not be available for flights, said a Lufthansa spokesman.
He said no intercontinental flights would be cancelled.
The open-ended strike began on Monday and hit Germany's largest airports, including international flight hubs Frankfurt and Hamburg.
The impact of the strike by members of the Verdi services union would grow in coming days, said union officials.
Verdi said the strike would spread to Berlin's two airports, Tegel and Schoenefeld, as well as Stuttgart and Nuremberg.
Some analysts have put the cost of the strike at about 5 million euros ($7.85 million) a day for Lufthansa, Europe's second-biggest airline by passenger numbers.
Like other airlines, Lufthansa is under pressure to keep costs down due to soaring fuel prices.
"We have had 1,000 flights fly so far today without any major problems — no cancellations and only a few minor delays," the Lufthansa spokesman said at midday.
Television pictures showed planes taking off as usual and departure boards indicating only short delays. Lufthansa said it had limited the impact of the walkouts by taking preventative action, such as re-assigning non-striking staff to other tasks.
"Today we have come through relatively well. It is difficult to predict how things will look tomorrow or on other days," the spokesman said.
Verdi said the aim of the strike was to hurt the company rather than to cause many cancellations.
German media reported many passengers had turned to other airlines rather than risk delays with Lufthansa.
"Our strike is going very well," Verdi negotiator Erhard Ott told ZDF television, adding that cargo, maintenance and catering had been hit.
Verdi, which represents 52,000 airline industry workers, wants a 9.8 percent pay rise for one year. Lufthansa is offering 6.7 percent over 21 months and a one-off payment. Ninety-one percent of union members backed the strike in a ballot.
Other unions have said they will not join the strike, among them the UFO union which says it is the main union for cabin crew and is demanding a 15 percent pay rise for its members.
Several German unions are seeking more pay because of rising inflation in Europe's biggest economy.
