I didn't want to blame Klax for this OOM
I hope so, since KLAX doesn't have anything to do with it...
I have Zurich, Chicago and Las Vegas from FSdreamteam. All complex airports. I think you use the same technology
Not really. KLAX is way better and more modern, although it's also more complex so, what you should expect is better quality and (especially under P3D) better fps at KLAX, a *bit* more memory used, but not nearly as much as you are reporting.
But read below: it's just wrong to compare two airports in very different areas. The only meaningful comparison would be FSDT KLAX against another scenery for KLAX, even the default one, with 0% AI traffic, because default sceneries attract less AI airplanes, so they will appear to "save" memory just because of that.
No problems with these airports. So I wondered why it is with KLAX.
An usual error, which is easy to do, is to blame an airport because you are "there", assuming that, just because you are there, it "must" be the airport.
But that's not how FSX works. When you are on any airport, all the scenery outside the airport is loaded too, with autogen, terrain, landclass, vector data like coastlines, roads, road traffic, and of course AI. All of this is NOT part of the airport scenery, but it WILL take away from your VAS.
Even if I start with the starting plane in p3D (and in FSX too) or the ultralight the use of memory shoots up to 3.1 Gb.
I already indicated a post with precise measurements of memory occupation at KLAX. This means, your memory consumption is not caused in any way by the airport. Also, it's very strange that you see the same amount both in FSX and P3D, since they are very different in this aspect.