Hi all i'm using Fsbuild to create my flight plans and i have a question about flight level to use because the program usually set 37000 feet in every flight i create.But i know that depending direction country and Nm of the trip there are correct fly level There's any guide to find the correct altitude to use in IFR with commercials airliners using high airways?

Here's some useful info:http://en.wikipedia.org/wiki/Flight_level

Hi all i'm using Fsbuild to create my flight plans and i have a question about flight level to use because the program usually set 37000 feet in every flight i create.But i know that depending direction country and Nm of the trip there are correct fly level There's any guide to find the correct altitude to use in IFR with commercials airliners using high airways?

I believe there is an altitude entry box just left of the default that FSB shows. Just type in your flight altitude of choice.

It depends on where you are flying, just to make things interesting.In the US, between 000 and 179 inclusive, you fly odd flight levels and 180 to 359 inclusive you fly even flight levels. That pertains to IFR flight. For VFR, the same rules apply above 3000', except you add 500' to the altitude below FL180.

Let me be more clear I will make you an example. IFR flight plan 300 nm fsbuild give me an altitude of37,000 feet FSX default flight planner 25,000. Speaking with a friend flight controller told me that usually in this case usually i have to to use an altitude between 29,000 and 31,000 feet for an optimal cruise speed at mach 0.78.Since 25,000 are few for a cruise of 0.78 and 37,000 are too much because i have to start descent almost immediately after climb, I was wondering under what parameters it calculates the optimal altitude for a commercial flight.Thanks for responses