Still the German airline is making it clear it's up to the union to return to negotiations.
Lufthansa has canceled about 1,200 flights Friday, two-thirds of its schedule. Ads in several German newspapers on Thursday said: "We regret this very much and apologize for it."
The airline added: "We consider this strike disproportionate."
On Tuesday, several-hour walkouts by Lufthansa cabin crews in Frankfurt, Munich and Berlin caused about 350 flight cancelations.
Lufthansa and the UFO union are at odds over pay and conditions as the airline struggles with increasingly tough competition from European budget carriers and government-owned Gulf airlines. Lufthansa underlined hopes of "more competitive structures in future."
(Copyright 2012 by The Associated Press. All Rights Reserved.)