|The following information is a rumor and/or fan speculation. Do not take as canon.|
The Sky Realm is unofficial realm but theorized to be one of the 4 unknown symbols.
This Realm takes place in the atmosphere above ground. There are also realm hazards. Harsh winds and the bright sunlight are the few hazards in this realm, in order to win this realm you need to be balanced and you need to be focused where to land after the big jumps. The track starts at the Exosphere and ends at the Troposphere. The skill for this realm seems to be driving in a progressively thicker atmosphere and finding out where to land while being blinded by the sunlight.
Sky Realm Accelecharger "Air Glide": Gives your car the ability to fly in the sky and over objects.