We fixed a bug (a real bug) in the terrain in Air America. Then we promptly sent you the buggy version instead. We will send a fix but here it is if you wish to fix it yourself. It puts a big lake where you have to land.
In the VietnamSEA_DATA.INI file in your Terrain>VietnamSEA folder, the last line is missing. Put this in place of [Texture121]