Can someone explain to me what are of jet and victor airways, their purpose and how to use them in FS2004?
Could you be a little more specific, a link to a site perhaps.
I'm editing my dumb answer. I'd better be awake next time.
Jet airways are above 18000 feet, and are intended as routes between major cities. Victor airways are below 18000 feet, and run between VORs. When you file a flight plan with ATC, you specify the route that you will follow between your departure and arrival points, and this route may include J or V airways. To use the airways properly, you need charts, but you can fake it by letting the sim select your route, and then following it using VOR and/or GPS. Hope it helps.
I always use the high alt. enroute charts.