Lufthansa, the second largest airline in Europe has canceled 3,800 flights due to their pilots going on strike beginning on April 2nd. The strike is centered on wages. The cancellations, which will affect more than 425,000 people, should only last through April 4th. The pilots? strike affects about one in every three flights that the airline had scheduled. The last major strike by the pilots was February 2010, but Lufthansa suffered a strike by its catering, freight, and maintenance personnel in April of 2013.
See "Lufthansa Scraps Majority of Flights as Pilot Strike Looms (1)", Andrea Rothman, Business Week, March 30, 2014