German airline Lufthansa cancelled nearly 900 flights Wednesday, at the start of a three-day pilots' strike, and is expected to ground 3,000 additional flights. The strike, which is possibly the largest walkout seen at the airline, will also be one of the biggest stoppages in recent years. Lufthansa's management and pilots' union Vereinigung Cockpit have been negotiating changes to retirement benefits. The union announced the strike after talks came to a standstill over the weekend. Despite the strike, the situation at the Frankfurt Airport seemed calm as passengers had been informed in advance of the flight disruptions. Lufthansa said it was attempting to book passengers on other airlines or train services to minimize disruptions to travelers' plans. Lufthansa has attempted to reduce inconvenience faced by passengers by informing them via text message or email, and providing sleeping arrangements and food at large airports, in case passengers did not get the warning messages. Lufthansa expects the strike to impact profits "in the range of tens of millions of euros." The airline's budget service, Germanwings, and its freight carrier, Lufthansa Cargo, have also been affected by the strike. Other subsidiaries of the airline, such as Austrian Airlines and Lufthansa Cityline, are not affected by the strike. Management and pilots have been squabbling over changes made to retirement benefits, including raising the retirement age and requiring new pilots to pay into a transitional pension fund. Lufthansa has faced strikes over the past two years from various unions over issues including wages, working conditions, benefits and the use of temporary staff. Vereinigung Cockpit represents between 85% and 90% of the 5,400 pilots who fly for Lufthansa and its related airlines.