It’s Sunday! This means Airberlin is running their SuperSunday promotion from 01-06PM (german time) .
Today they offer national german routes only mostly from and to Berlin or Hamburg. For detailed routes see promotion page.
Luckily airberlin also publisched a list of dates and routes when their promotional price should be available: Routes and Dates
Bookable: 22.05.2016 13:00-18:00 Uhr
Travel by: 01.06.2016 – 04.09.2016