Talk:Winter 2019 Event/@comment-26823646-20190106190020/@comment-26082284-20190106201543

You can calculate cumulative chance for N number of sorties.

For example on easy it's about 25 S-ranks to have 50% cumulative chance and about 80 S-ranks  to have 90%. If you are unlucky 6% it'll take more than a 100 S-rank sorties.