This code best works when using a warthog. you have at least two people in the warthog and drive over to the other base and go below the base (where the banshee usually is)if the banshee is not there then park the warthog where the banshee would go. then have the passenger get out of the warthog and jump either on top of the banshee or the warthog, at this time you should be directly under the flag. jump up and it will say press x to grab flag. grab it through the floor and get back into the warthog. you should be home free.