OK I just tried it last night... for the heck of it.
I didn't try to disable anything.. had about 40 processes running.. 1.6 Atom Processor, 512MB RAM, XP Home, 120GB NON-SSD drive, Intel Integrated GFX. I also left A/V running (AVG Free right now) for some kind of a baseline.
1024X600 Resolution, 128 Textures, All advanced AH GFX options off (except bump), and sliders all the way down...
Ready for this?
You sure you want to know?
17FPS (Offline mode sitting still on runway). If I look straight up, I can get 30FPS.
I took off, flew in a pattern and then tried to land (if you think flying with a mouse is hard, try a touchpad)... It stayed pretty much 15-20FPS the whole time. Turning off bump didn't improve performance any.
I figure if I trim do the processes and turn off A/V it MIGHT see 25 fps or so... which might be acceptable IF there is no stuttering... but something tells me that's not likely...
I'll let you guys know when I run some more tests...