Comment 1 for bug 736479

/etc/lftp.conf from Debian (ubuntu might be the same) is:
# try inet6 before inet
set dns:order "inet6 inet"

which is also the default lftp(1):
       dns:order (list of protocol names)
              sets the order of DNS queries. Default is ``inet6 inet'' which means first look up address in inet6 family, then inet and use
              them in that order. To disable inet6 (AAAA) lookup, set this variable to ``inet''.

lftp tries to connect first to IPv6 and then v4. The connection still works (after the v6 tries).
But correct me.;)