During the nine days, many hold that we refrain from activities that are considered even slightly dangerous; for example, air travel.
However, I have read that R' Shlomo Zalman Auerbach (who generally held that one should not fly during the nine days) considered it justifiable to fly to Israel during the nine days because of the additional mitzvot one may fulfill there.
Are there other recorded exceptions, of situations where one may undertake a "dangerous" activity that we would otherwise refrain from during the nine days, to fulfill a mitzvah? (For example: air travel during the nine days in order to attend a levayah?)
Conversely, are there recorded cases where we are told not to undergo some danger during the nine days, even if this means missing an opportunity to do a mitzvah?