I am not expert on scenery development, but I've been trying to correct and improve my local airport (Jundiai - SDJD). The default airport altitude is almost 500ft above than it should be. I edited APX file and it corrected only runaway and a small area around it. The region around airport boundries is still high. I tried using flatten area with SceneGenX software, but it did not work. I realize that flatten areas generate and separeted .bgl files. Maybe FSX does not read this files.But when I use airport polygon (APRON) it works as a flatten area. Sure it's not pretty to use APRON to flat region around airport boundries because APRON is covered by a texture.Any suggest is appreciated.RegardsBruno

You need to exclude the default flatten and create a new one using Shp2Vec. See the first sticky topic above.George