Ludwik asks about balloon sailing. Clearly practical balloon sailing
depends on choosing the correct altitude for a desired result.
I believe a balloon could also sail "into the wind" if it operates in
a region including a wind velocity gradient and has extent sufficient
to exploit the difference. I doubt the value of expending engineering
effort on this enterprize, but I have heard of it being done for kites
which have flown free for long distances, though not against the wind.
The essential difference between the balloon and boat-car cases is in
the extraction of energy from a system in which a velocity difference
in the media exists and one in which none exists. In the ballon case
it is simply more difficult to exploit this velocity difference.