Barret mentions it, as well as a few NPCs in Cosmo Canyon and around Midgar. It's also stated in the Ultimania Omega how Barret's "New" AVALANCHE was inspired by the older one. Barret talks about said inspiration as well. The original founder of AVALANCHE who fought Shinra started the group in Cosmo Canyon.
*The anti-Shin-Ra organization*
One who participated in the Study of Planet Life began to question the conduct
of Shin-Ra due to their use of the Planet's Spirit Energy as mako. To protect
the life of the Planet, they began anti-Shin-Ra activites in various places.
Extreme conduct would follow on their part, and the explanation of Shin-Ra's
faults that they offered held that the life of the Planet was more valuable
than that of humans.
(Accompanying screenshot caption 1)
The anti-Shin-Ra organization AVALANCHE -- whose activites were aimed to
disrupt Midgar -- had the power to serve as an obstacle to Shin-Ra.
(Accompanying screenshot caption 2)
The AVALANCHE seen in the game was the new AVALANCHE, of which Barret was the
leader. Their base was the Seventh Heaven bar in the slums of Sector 7.
Suffice to say, Shinra had been dealing with this threat before, and they raised hell. Even better than Barret.
Even assuming that this is true that that people in Midgar and Junon really are absentminded to not notice an invading force with most of them having an extremely popular public figures hair and face, you still would figure that someone, if not many people, would bring up all of these battles in their urban centers.
LOL. Well, remember that most Genesis Copies wear masks, dude. The only ones that don't are the specialty ones like the G-Gunners, and G-Paladins. The grunts of the Genesis Army usually wear masks. And the freaky ones, usually are so ugly and disfigured that they don't even look like Genesis at all anymore. Maybe those that did bring up the fact they looked like Genesis were summarily threatened or made to "disappear" like those who knew the truth regarding Nibelheim.
People today are still talking about 9/11, and after events such as WWII, people in Stalingrad, Berlin, Kiev, scars of the battle, physical and mental dominated people's minds and conversation for years. People in FF7 don't really say shit about it. And you can cover up why a battle happened, the antagonists, and the details, but you can't hide or cover up a battle itself, so that's out of the question.
Well again, some people in Midgar do say that they heard of AVALANCHE before in the past and think its all stupid so...
Didn't the Turks fight Jade WEAPON in Midgar? Or was it Zirconaide? Either way, I know the Turks had SOME huge battle with SOMETHING in Midgar.
Jade WEAPON can be fought anywhere. From a populus place like Midgar, to an isolated area like Icicle Lodge. Depends on where you are in terms of service. And yeah, I'd equate that fight to how you ran into Deathguise in FFVI. It's stalking the skies and shit, but not many people say anything about it despite the fact its *there.* Most people just probably see it as another monster, since its only attacking people in the air, or whoever it sees as a target. It's not causing wanton destruction like Ultima WEAPON.
EDIT: So it had to have been Zirconaide. Even so, wouldn't people notice a huge monster jet flying around? People sure noticed Doom Gaze in FF6.
Well, monsters do attack in the world of FFVII. They probably saw it as that and due to the fact that Zirconaide wasn't allowed to become fully complete, it wasn't nearly as much of a threat as it could've been. The Turks were able to keep it as low key as they could before it became a huge threat like the WEAPONs in FFVII.