Mesh has invisible parts after exporting This is my mesh in Blender:



And this my mesh when placed in UDK:



As you can see it doesn't have the human head/chest part, parts of the hood are invisible, and it has some white lines. Why?
It looks like:


The human mesh's normals are flipped. You can correct that by selecting all of it in edit mode (A) and then pressing CtrlN
The hood/robe mesh has no thickness, so parts of it will disappear due to backface culling. You can fix this by adding some thickness with the Solidify modifier.