FS2004 Route

[runibl]

1. Direct GPS is simply a direct route from a to b.
2. Low altitude airways is mostly for props flying low.
3. High altitude airways is mostly for jets flying high.
4. VOR to VOR, is as it sounds using VOR waypoints for navigating.

Option 1 is not realistic, but is good if you just wan't to go directly to destination. No detours and waypoints in between.
Option 2 and 3 is propably the most realistic ways to fly IFR using airways.
Option 4, maybe there's no airway that gives the most optimum route to destination. Then this is the option to go by.

If you wan't realistic routes, you should try these:
For real world routes in use in USA. (Drawback is it only supports USA)
http://flightaware.com/analysis/route.rvt

For routes in Europe, Africa, Australia and S. America. Select departure and arrival, and it will check for routes on the internet and you can save
flightplan to use with the GPS. Requires online connection to work. It is a free program, but doesn't support rest of the world.
http://www.euroutepro.com/

This is a great place to create routes, input departure and destination. Then it will find the route for you. It has many options to use and it
supports the whole world.
http://rfinder.asalink.net/free/

After finding a route and you want to save it as a flightplan then use this. It can export flightplans various formats including LVD 767, PMDG 737 and
FS9.
http://www.fsroute.com/