My idea is to make static aircraft part of the scenery, like a building or a tree or something. They would still exist, but they would be part of the taxiway, or background. That way, there's no separate aircraft textures or .air or .cfg files for the PC to have to deal with, 'cause that all gets loaded with the scenery.
No, the fde files don't make any difference - it's the textures that matter. Your statics will need em (see below).
Lots of buildings also make FRs drop. But bear the following in mind.
Nearly all FS default building textures are 256x256 8 bit bmps and each building only has one texture (composite for all 4 sides + roof) which is why default buildings are v poor quality when you view em close up. But you can add a lot of buildings like that before the prog starts to get bogged down.
With 'featured' airports like LHR, LAX, detail has to be increased so bigger textures are used. These hit fr and when we use AFCAD to put more AI in, that's why fr drops to a crawl at those places.
Default aircraft (inc the ones that are used for AI) are 1024x1024 ext bmps with MIPs but there's only the one texture plus a decal texture per aircraft. But you can see as soon as you add more default AIs you're adding some big texture files which is again why the prog slows down.
Because people want quality, most 3rd party aircraft use 512x512 ext bmps with MIPs for their detailed bits plus some smaller textures (eg 256x256) for the less detailed bits (eg gear etc) but as each plane will have prob at least 5 or 6 512x512 textures, you can see they will have a big impact on fr when they are in view (as AI or even in spot view). People like Aadvark have made their mark by dispensing with the MIPs which obviously reduces the texture size for their planes with a loss of detail at distance, which of course we don't care about for AI.
So you can see where this is all going. People WANT to see quality - they can ONLY get it at the cost of cpu processing power because quality means large texture files.
And I haven't even begun to talk about the impact of lots of animated bits on aircraft (doors, engine covers, holds, flaps, gear, flexing wings, rudders etc) which slow things down even more because with each cycle the machine has to check that as they are there, have they been activated (yes/no) and if so, what is their current status/position......
Hope this helps to explain things a bit.
Roger