I just thought of this, but has any body ever thought about what causes and maintains the flux field/vortex around the Tree of Souls and around the mountains? I think that it is caused by the Tree itself. Look at Pandora as a giant computer network and the Tree of Souls as the central hub and Ewya as a sentient AI. any large electronic item such as an AI, ect. uses a large amount of electrical energy, which, when run through uninsulated wiring, creates a magnetic field, that is the basis of electromagnets. As far as I know, there is no electrical insulation or Pandora's equvalient around the Tree of Souls. Out in the rest of Pandora where the connections are from tree to tree and run through the root system, the Tree is a giant unshielded input piece of the system. The way I see it, with the Tree being the focal point, that area is like a giant EM field and it is acting like a radar/sensor jammer to any unshielded vehicles. This is my take on the matter.