What is the best free flight simulator

I know one game,but yow have to be a bird to play.It's called "Fly Like A Bird"The best one,in my opion,is FLAB3(There is no FLAB4 so far.)
You can eat,make nest,fly(very good flight)in FLAB3 you make nest and eat,along with better flight,more birds,more places,better chat,and better graphics.It plays in your browser.I have not been on lately,and my brother says it has changed so if you don't like it or something i said isn't there,don't blame me
And always keep looking for the game that's perfect for you!