( CNN ) -- The pilots ' union of Lufthansa began a strike Monday after a last-ditch effort at negotiations over pay and job security failed , a spokeswoman for the airline told CNN . The four-day work stoppage by the pilots ' union of one of the world 's largest airlines threatened to disrupt travel on more than two dozen partner airlines later on Monday . Lufthansa and the pilot 's union , Vereinigung Cockpit , met over the weekend as a last-ditch effort to avoid the strike . More than 4,000 pilots walked off the job at midnight Monday ( 6 p.m. Sunday ET ) through Thursday over protracted contract negotiations centering around pay and job security . The action by Lufthansa pilots signaled growing labor unrest across Europe . The industrial action by the pilots started the same day that British Airways cabin staff were expected to announce the outcome of its strike vote . On Wednesday in Greece , a mass public and private sector strike is being planned to protest the government 's austerity plan . Lufthansa had already canceled two-thirds of its scheduled flights Monday to Thursday ahead of the strike . The bulk of the disruptions are expected to begin later Monday since most German airports prohibit flights overnight . Still , passengers at Frankfurt Airport on Sunday were already feeling inconvenienced . `` It makes me angry because for me , normally I would ( leave ) on Monday morning , '' said one passenger . `` Now I have to go Sunday evening and my family 's at home and I have to ( return ) tomorrow night with the train . So it 's uncomfortable . '' `` It 's inconvenient and it 's not justified at all , '' another passenger said . Company officials admitted it would have a `` heavy influence '' on its international operations , which includes flights to 80 countries worldwide . Send your views and experiences to CNN iReport . In 2008 , Lufthansa was the number two international carrier by passengers with 42.2 million , according to the International Air Transport Association . The threatened walkout came as the airline industry is digging out of the worst one-year drop-off in flights , according to IATA . In 2009 , revenues dropped nearly 15 percent worldwide after generating a record $ 535 billion the previous year . Passenger travel fell a record 3.5 percent and freight fell more than 10 percent , according to IATA figures . Lufthansa officials said at a news conference last Thursday it would cost the airline about $ 33 million a day . Many of Lufthansa 's pilots have been working without a contract since March and more than 90 percent of the union 's members voted to strike , said Jorg Handwerg , a pilot and representative for the union . The union sought a 6.4 percent pay increase . The union is also concerned with the airline 's recent buying spree of small regional carriers , such as BMI and Austrian Airlines which , it says , is cannibalizing flights away from union-flown routes . `` We fly less hours and have less potential for ( performance-related bonuses ) , '' Handwerg said . `` We want to have the opportunity to grow , but instead it shrinks . '' In a statement , Lufthansa said : `` In addition to demands on job security , however , the union also insisted on a greater say on fundamental entrepreneurial issues , equating to intervention in business management at the airline . That demand can not be accepted . '' The airline is allowing passengers to rebook flights for tickets purchased before February 18 and plans to give German domestic passengers rail vouchers . But one Lufthansa passenger said she is having trouble reaching a compromise with the airline . `` I spent several hours on the phone with Lufthansa to try and figure out what I can do , but now I 've been told that I ca n't even get a refund , '' said Ruth Winblad , who is supposed to fly Monday from Gothenburg , Sweden , to Rome , Italy . Lufthansa is one of the largest carriers on Star Alliance , a network of 26 airlines that share ticketing and routes for international travel . Travelers on Star Alliance flights are advised to check their tickets for Lufthansa flights and contact their carrier about any potential changes , said Markus Ruediger , Star Alliance spokesman . Star Alliance member airlines are : Adria , Air Canada , Air China , Air New Zealand , ANA , Asiana Airlines , Austrian , Blue 1 , BMI , Brussels Airlines , Continental Airlines , Croatia Airlines , Egypt Air , Lot Polish Airlines , Lufthansa , Scandinavian Airlines , Shanghai Airlines , Singapore Airlines , South African Airways , Spanair , Swiss , Tap Portugal , Thai Airlines , Turkish Airlines , United Airlines and U.S. Airways . Partner airlines were preparing for the strike . `` Some of our codeshare flights with Lufthansa may be affected during the period of the strike . We are in contact with Lufthansa and will be informed of the affected flights as soon as details are made available , '' said Nicholas Ionides , Singapore Airlines spokesman . `` Should there be customers traveling on affected Lufthansa-operated codeshare flights , they will be contacted and re-accommodated on the best next available schedule . '' A spokeswoman for Continental Airlines told CNN on Sunday that the airline will offer passengers refunds or rebook their travel if they are affected . CNN 's Kevin Voigt , Stefan Simons , Phil Han and Greg Morrison contributed to this report .
NEW : Estimated 4,000 pilots at German airline Lufthansa begin four-day strike . The pilots union says strike focuses on pay and conditions issues . Germany has been hit by a series of strikes in recent years over wage increases, pensions and other labor matters. Lufthansa flies to 80 countries with its main hub being Frankfurt , Germany .