The problem mentioned here by Bucksfan is not solved by the mesh adjustment file in FS Global 2010/FTX Vector. I have the same problem using the AES adjustment file and without it (though it is much worse without it).
As already explained in many other threads about this issue, if you use a 3rd party mesh, you must FIX THE MESH, or just stop using it, because the problem doesn't exists with the default mesh, since the default mesh has been correctly pre-processed by Microsoft to be adjusted around airports. Your 3rd party mesh should have been pre-processed the same way.
The real cause of the issue, is that FSX doesn't support sloped airports, and KLAS IS SLOPED in real life but, since FSX doesn't support it, not without entirely messing up with the AI traffic and the AFCAD, all FSX airports should be considered to be flat and of course, we don't have any other choice than representing the airport to be flat as the one and only sensible value, which is of course the published airport QNH, and KLAS is obviously correct in this regard.
However, since that real world area is NOT flat, if you use a 3rd party mesh AS IS, you WILL see a difference in altitude because the real world area is sloped, while the airport is flat, and must be flat, for all the aforementioned reasons that the FSX engine doesn't really allow sloped airports.
The FSX default mesh has been preprocessed to smooth out the differences in altitude over an airport surface, so you won't have such problem with the default FSX mesh. But 3rd party meshes aren't usually pre-processed this way, which is the whole point of ADDITIONAL products designed to FIX this issue which, again, happens at the MESH level (the airport can't be fixed)
Now, I don't really have any idea why that fixer mesh doesn't work but, you are referring to a 3rd party MESH fixer that is supposed to fix another 3rd party MESH problem. The airport doesn't have anything to do with this, you should enquire to those that made the fixer and ask why that fixer doesn't fix the mesh.
I have nearly all other of Your airports, but none have the problem and adapt nicely when you use the AES file posibility, so it is only KLAS that cant be fixed.
It's NOT the airport that is supposed to be fixed here! That fixer is a fix for the MESH. The product that can't be fixed here is the MESH, not the airport, the whole point of these products are to fix a mesh in order to adapt it to the airport, not fixing the airport.
The one thing you can TRY, is to remove the mesh_terrain.bgl file from the KLAS scenery folder, and see if you have an improvement. This file is supposed to precisely use it with 3rd party meshes which hasn't been pre-processed correctly, but perhaps it might be better if you remove it when using it with a mesh FIXER product, so you are not "fixing the fix".
If you don't have it, perhaps you removed it long ago, then it would be worth trying to restore it ( it comes with the KLAS installer, so you can restore it by reinstalling KLAS).
