Exo One

An alternate way to get this achievement is near the end of the level, in the really mountainous part of Gnowee. There are two red gates, which are very easy to see if you clear the fog layer. Passing through either one could give you enough momentum to break the sound barrier for at least 5 seconds, though it might take a few tries.

(On a side note, I was not able to use the red gates to also get the height achievement at the same time. They are too shallowly oriented.)

This one can be tricky, but getting the right boost will get you this achievement and the Get High achievement for this level. In the last area of Gnowee there are lots of very steep mountains and valleys, if you can angle down one to pick up momentum then up an adjacent mountain you will get insane speed when you glide as well as going extremely high.