Unfortunately the progress for the new training was patched.
This method works.
I started a one-man-squad match on the oceanic server.
(Depends on your time zone, choose a server, where nobody should be)
After 6 or 7 minutes, the lobby started and I was the only gamer in this lobby.
As the plane flew over the beginning of the take-off line, the match ended and the achievement for winning in squad popped for me.
I already got this achievement in the training mode,
so I cannot (!) confirm that this method works for the progress of this cheevo, but It should (!) work.
General Sengir progress counted 20% per match.
P.S.; If you vote negative, write a comment or send me a pm for your explanation, please.