iBlah on 26 July 2012
the chopper Batman used was hidden on a rooftop, it makes sense for other choppers to be hidden on rooftops as well, bad guys only managed to break into the vault, but there were hundreds of thousands of rooftops in Gotham for Fox to hid his choppers, since he was in charge of the company that built half the city.
Even if they did find them, keep in mind that Bane only had a small amount of followers in the beginning, the majority of his army were common Gotham thugs that got busted from the jail, it is unlikely any of them can fly an ordinary chopper, let along the uber expensive ultra complex badass prototype Batchopper.
