BERLIN (AP) — A cabin crew strike at Lufthansa will expand on Wednesday to affect all of the German airline’s flights in an escalating dispute over benefits.

A union representing the flight attendants called Tuesday for its members to widen the strike, which began Friday at Germany’s three main airports. Tens of thousands of passengers have been affected so far by hundreds of cancelations.

Lufthansa confirmed Tuesday that all of its flights from Germany would be affected from 4 a.m. (0300 GMT) Wednesday until midnight Friday.

The UFO union wants to secure transition payments for its 19,000 members if they retire early, among other demands as part of its contract dispute with Lufthansa, which is trying to cut costs.

The union rejected the airline’s latest offer Monday, saying it constituted only a “minimal” improvement. UFO representatives noted Tuesday that the airline recently increased its pre-tax earnings forecast for the year.

Flights operated by Lufthansa subsidiaries such as Germanwings, Swiss and Austrian Airlines won’t be affected.

Photo Credit: Cancelled flights appear on a board in a terminal of the airport as flight attendants of Lufthansa airline went on strike for the fourth day in Frankfurt, Germany, Monday, Nov. 9, 2015. Michael Probst / Associated Press