Yeah there plenty of working vehicles in the factories, but the surviving forces are unable to reach them. As for air support all of it has been ordered not to launch until you confirm you have the package, as they don't want to fly into hell if there's nothing worth grabbing. Main force of troopers in this area are located at the an armory near the space elevator which was filled with warthogs and scorpion class tank along with enough ammo for a month. These are being used to stop the Covenant assault is the only reason why they have not seized the orbital lift. However most of the city is intact, just the fact that covenant have over run almost all positions in it and have pressed to take the elevator. As such the squad is dropping in on the far side while on cruiser distracts the super carriers and then jumps away before it can be destroyed.