If one is on a plane on Sunday night when the Tisha b'Av fast ends, is it possible to make havdalah on the plane in order to be able to break the fast? Airport security might not allow passengers to carry wine onto the plane, and in the US, even if wine is permitted, security might not allow a sufficient quantity.
The criterion for beverages for havdalah (and kiddush, and the four cups at Pesach) is that they be chamer medina, a "national drink" or something you would serve guests. According to the OU:
In a place where wine is not available, one may make havdalah on beer, mead, or any other beverage that is considered a local drink, excluding water. (source)
If you can't bring your own, you should be able to obtain a suitable beverage on the plane or in the airport beyond the security checkpoint. While you probably won't find kosher wine or grape juice, many commonly-available beers are kosher, and you might find apple juice. In my experience tea and coffee are universally available on planes. You should, of course, consult your rabbi about acceptable substitutions.
If you can bring your own wine or grape juice, and the only issue is, in the US, the permitted amount in a container of liquid, you might actually be ok. According to this source, in the name of R' Ovadiah Yosef and R' Eliezer Melamed, a revi'i is 75ml rather than the older calculation of 86.4ml; both of these are below the TSA limit of 100ml. (h/t DoubleAA for the source and sizes.) You could also divide a larger amount between two containers or combine with a traveling companion.