German airline Lufthansa has announced that it is canceling 1,000 flights on Wednesday, September 9, 2015 because of a pilot strike.

Approximately  140,000 travelers will be affected by the grounding, the airline said Tuesday. “Lufthansa deeply regrets the resulting inconvenience to its customers,” it said.

The pilots union, Vereinigung Cockpit, began its strike on long-haul flights Tuesday, forcing the cancellation of 90 flights. On Wednesday it is extending the strike to include medium- and short-haul flights.

Lufthansa says passengers should check its website at www.lufthansa.com/de/en/Travel-information for details of forthcoming flight cancellations.