There is no legal requirement to announce a strike in advance, but VC seems to announce them between 12 and 72 hours in advance anyway. And even then only domestic flights or flights leaving germany are on strike, those returning to germany are not part of the industrial action, however lufthansa might elect to cancel them anyway to keep the rotation going, or to keep aircraft piling up in frankfurt or munich.
@highflyer: it is not about a pension that has to be paid open end, it is mainly about transitional pay that is paid out for a maximum of eight years, average of only four years.