Great audio and art but lack of direction (yes im aware of the minimap UI). Since it's already hard to control the paper plane--which I'm sure is the intention, give the player some leeway by granting them a visual cue of where to go besides relying on the minimap. Maybe highlight the object that the player should go to or implement a beacon of sort on top of the destination.
This is my personal opinion so don't take this the wrong way or anything like that but I feel like the minimap was not necessary in this game because as it is now, the player (me) would have to rely on the minimap, focusing most of my attention on the minimap in order to guide the plane rather than focusing on the world itself. The symbols next to the timer is not conveyed properly. I suggest a fade-in/fade-out small text on the screen with a one-word description like "Updraft" or something along with the symbol.
Overall, a cool game. I'm happy that you got it all working. Feel free to argue with me, but know that I'm just giving you criticism and it's not meant to be taken personally. :)