I found this great site today that allows you to plan any flight in the world. It's really easy to use and gives you a map of the route when done.
You type in your route (from/to airport) between any 2 points in the world and specify altitude, speed and aircraft range etc (If the route is beyond range it will schedule refuelling stops)
You can even specify the airports used must have ILS or a runway of a certain length, and you may use eithere high or low altitude airways
It will calculate the trip and even shows a map of the route!
Check it out;
Let me know what you think!