Number 3 would get my vote - don't love the shape though.
What I would do: wear leggings and cardi on the plane, take them off at arrivals (there are bathrooms where ou can do this). Do yourself a favor and get natural fibers only - polyester is vicious in the heat.
I live in Italy and just travelled the other way (South->North) in this sleeveless shift and bare legs. Was not cold, wore a cotton cardi on the plane, had a trench coat for the taxi ride in my bag but did not need it. Chose the dark denim color because of the DC (once wore a white T shirt, guess where DD1 wiped her tomatey hands)...