Hello!
Is there any way to remove trees and buildings. I dosn't look good when its growing a tree in the middle of the runway!

Right on Wji. 

BEFORE EDITING THE scenery.cfg file, MAKE A COPY AND PLACE IT IN A SAFE PLACE

There is no 'altitude' with an Exclude file that is contained in the Flatten string
Here's an example of a scenery.cfg entry I created:

[Area.137]
Title=North Cape, Siberia
Local=Addon Scenery\North Cape, Siberia
Remote=
Active=TRUE
Required=FALSE
Flatten.0=60,N68 54.42,W179 30.50,N68 54.42,W179 27.48,N68 54.35,W179 27.48,N68 54.35,W179 30.50
Exclude=N68 54.46,W179 30.66,N68 54.35,W179 27.48,all
Layer=138

Here's how I make New Airports
I use AF2 and FlattEx

1.) create a new /scenery folder for the AF2 file
2.) start FS9 and allow it to "Build Scenery Files" (this creates a new entry (appends) to FS9/scenery.cfg)
3.) Create Flatten and Exclude using FlattEx (viewing aircraft position in AFCAD2)
4.) Copy&Paste FlattEx coordinates to scenery.cfg file
5.) Reload FS9 and view masterpiece
6.) Edit AF2 as required
7.) Add scenery objects using Abacuspub's EZ-Scenery