This is all unfortunate, but understandable. Surveys of women who travel for business have found that staying safe is their biggest concern. It is difficult to find statistics on how the perception of danger while on the road matches up to the reality. But that is not necessarily the point. If some women feel vulnerable when travelling alone, they have the right to have that uneasy feeling countered.
Still, it is a conundrum. Segregation might be a short-term solution, but it is no answer if we want to change attitudes in the long term. Much better to mitigate the causes of the problems, rather than simply hive of sections of travellers. Take the Air India case above (the details of which are still far from clear). In a similar situation, solutions might range from placing solo women next to families, to questioning why on earth a man might want to swap a business class seat for one next to a young woman flying on her own.
There is a further issue. The more others are segregated from us, the more we expect similar treatment for our own clans. El Al flights, for example, have been disrupted in recent years as haredi (ultra-orthodox) Jews have refused to sit next to women who have been assigned an adjacent seat, as their faith prohibits contact with a non-related female. Planes can get stuck on the runway as the innocent women are pressured (sometimes by employees of the airline, it seems) into swapping seats.
One mooted solution has been to have an area in the cabin set aside on El Al flights for haredi. But that is a slippery slope. If everyone got their way, and cut themselves off from those who offended their sensibilities, planes would soon run out of space. Some Asian carriers have now introduced child-free zones where passengers can put distance between themselves and anyone inconsiderate enough not to have grown into a fully functioning human being.