unity3d animation co ordinates changes

hey every one,,i'v one peculiar problem...basically i'm trying to make a animation of a object using unity animation..so its an aircraft flying in a particular direction in a terrain,after animating,i try to export the whole project,,but when i do all the co-ordinates in the animation file changes and now animation playing outside the terrain,hmm i thought it might be some problem and again did everything from the beginning,now again same problem ,,but the animation playing a bit away from the terrain,is it a bug in 3.2 and also i'm using a terrain of 8000x 8000 resolution,that causing any problem?? i even tried to make prefab's and put the game object inside,and even tried to make empty gameobject and tried,,still no use,,am i doing it wrong?? thanks in advance