frame rate

hi guys, I am new in this thing of adding flight routes and aircraft into airports.
I have the following problem. I have added some traffic into airports but the problem is that my frame rate now is crap, is there anything I could do to improve this.
I have a 900mhz and 256ram computer. Is this to slow for adding extra traffic in airports?

I have the following problem. I have added some traffic into airports but the problem is that my frame rate now is crap, is there anything I could do to improve this.
I have a 900mhz and 256ram computer. Is this to slow for adding extra traffic in airports?
