Thank you very much Rainboe!!
Yes, I knew I had come to the right place for my question ehehe ...
Anyway, let me better understand...rhumb lines cut merdiens with costant angles, while great circles are the shortests tracks from A to B.
So I assume that when you fly great circles your track costantly changes, isnt this right?
Well, does your track changes when you're flying a NAT going, for example, from 40N20W to 43N30W ??
Thank You very much!