The flight attendants union called on its Lufthansa members to strike for 48 hours this week. UFO says the strike will start midnight (Central European Time) on Thursday and last until midnight Saturday.

Lufthansa announced in a tweet it condemns the UFO’s call to strike and is currently preparing to file legal action against it. In the meantime, the airline is working on a “special timetable” for flights Thursday through midnight Saturday. When Twitter users asked if flights would be canceled Lufthansa told them to monitor the account for updates.

Lufthansa is a major carrier in Germany with hubs in Frankfurt and Munich. The strike could mean trickle-down problems for subsidiaries Eurowings and SunExpress.

There are concerns this could cause problems with those heading to the capital this weekend for the 30th anniversary of the fall of the Berlin Wall.

This has been a long and messy battle between Lufthansa and UFO. A strike scheduled last month was called off at the last minute.

Flight attendants are fighting for better wages and pensions. Lufthansa has been fighting the union’s legal status.

In the meantime, if you have a Lufthansa flight, you should familiarize yourself with the European Union’s Passenger Bill of Rights if your flight is canceled or delayed.