It seems that (at least the new) ITA Matrix Search can do that as well: Once you select an airport (or city) as origin or destination, it gets added to a list o

It seems that (at least the new) ITA Matrix Search can do that as well: Once you select an airport (or city) as origin or destination, it gets added to a list of possible locations. Being used to Kayak‘s comma syntax, I did not find this intuitive at first. But in fact, it is pretty convenient and powerful.