1) CA can give a pilot control of the Battlefield vehicles on the F-10 map, if that option is set in the mission editor. You can enter a vehicle (RALT-J) but then the AI takes your Aircraft.
2) The player can play as Ground Commander, control ground and Air units from the F-10 map, can enter vehicles and control that group from the vehicle. And Enter JTAC mode when in vehicle
Please take the time to read the CA manual, it will make this a lot clearer.
Nate