May a husband and wife go with other ppl on a hot air balloon ride during bein hazmanim if the wife is a niddah? Is this similar to riding together In a car?
Without getting into the issue of taking a tiyul while she is a nidda, it would depend on how large the balloon is. If it is large and there are a number of other people there, then it would be like going in a large boat, which is permitted. However if it is small even if there is another person in it then it is problematic.