There's no regulation per se, it's whatever is in the fineprint when you purchase your ticket. They typically wave any responsibility if the reason for the dela

There's no regulation per se, it's whatever is in the fineprint when you purchase your ticket. They typically wave any responsibility if the reason for the delay is any of the following : bad weather, acts of God, terrorist activities, war, strikes, "any shortage of labor, fuel or facilities” and “any event not reasonably foreseen, anticipated or predicted” This could fall under "not reasonably foreseen" or maybe act of God for the very religious :).