Exo One

This one can be tricky, but getting the right boost will get you this achievement and the Speed of Sound 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 speed then up an adjacent mountain you will get insane height when you glide as well as going well over the sound barrier. I got so high I couldn't see the map anymore

Unfortunately we can't add images to comments, so I'm just going to write another solution here that includes details from both my own experience and the other guide. A workable solution might be a little easier to read with everything all together.

I found this one to be a huge pain in the butt, and I spent probably about an hour going for it.

As Darkwing666 says in the other solution, the way to do it is to get to the very last stage of Gnowee, after the large alien superstructure, where the mountains start getting really rugged and the valleys are filled with an upwards-pushing fog.

It is important to find a narrow mountain pass with tall parallel linear walls (not a bowl, and not an area where you have a large amount of flat ground in between two mountain slopes). There should be no hills or bumps in between the walls, and the valley floor itself should not be tilted.

I found one that was somewhere in between the first two pillars you pass by in the mountainous area. Get above the fog layer in this area to find a good position, and then, as Mastercheeks117 said (in a comment on the other solution), when you are above one of the walls, hold to become a marble. You should break the speed of sound as you catch the wall. Right when you pass the saddle in the valley, and you start going up the other side, release gravity mode and hold down only to become a disk and you will shoot really high above everything. Hold onto it for as long as you can glide. (If you fall back below the speed of sound before you are airborne for about two seconds, you probably aren't going to pop the achievement and should try again. This may have happened because you were in marble form for too long when you were getting launched uphill.)

It took me six tries after I found an area that worked.

(Strategies that did not work for me:
- using the red gates, which were too shallow.
- launching myself at a near-vertical angle through one of the pillars, which gives you a speed boost. The speed boost was never enough.
- Climbing to the very top of the really tall alien superstructure. It's tall, but it ain't that tall.)

PS: For some reason TrueAchievements isn't detecting the screenshot I took of where I was when the achievement popped. I will add it ASAP when it detects it.