Frankfurt Airport’s departure board showed that flights to the United States, India and Canada were among those canceled.
Customers can rebook on the airline for free within 10 days, Lufthansa said. Domestic travelers have the option to exchange their flight for a train ticket.
Lufthansa has roughly 135,000 employees and a fleet of more than 350 aircraft. It operates out of airport hubs in Frankfurt, Munich, Zurich and Vienna.
Lufthansa said that it would enter talks with striking unions, including the Independent Flight Attendants Organization (UFO), which is locked in a dispute with the airline over its legal status.
The union has accepted the offer of weekend talks and will then decide whether to undertake formal arbitration, UFO official Nicoley Baublies told Reuters.
The strikes will not affect other airlines in the Lufthansa group, such as Brussels Airlines, Austrian Airlines and low-cost carrier Eurowings.