true sky

Alto has some kind of obsession when it comes to the sky. One of his dreams is to fly free in a limitless sky, something that you can't actually do on a fleet since they're in space. Since he was only a child, Alto has always been trying to reach the sky and playing with paper airplanes, an interest that his decreased mother left to him before she died.

It's not difficult for him to explain how much he hates the artificial sky that they have in the fleet because Alto happens to be a pretty direct guy who'll always complain about the stuff he doesn't like and will try to change it. Also, the sky can have a lot of meanings when it comes to him. His dreams about flying can be related to some kind of spiritual meaning, trying to tell us that he feels trapped in what we call earth and tired of dealing with humans or his own problems. This theory seems to be pretty interesting, especially after watching the last episode in which Alto refers to Sheryl and Ranka as his wings, those wings that helped him to make his dreams come true and allow him to keep walking forward.

Alto Saotome flying in Frontier's limited sky, Ep.1 "Close Encounter"