Nice idea, the concept is really clever and I like the unique steering method by targeting the right altitude - that's a really cool idea.
In practice though, it was quite a hard game to play and I felt it might have helped having a more of a game friendly HUD to help with the navigation as the text weather report was quite a dry way of putting it. Also, given the balloon ride itself made me feel quite queasy (and I was sitting down), I also felt I had to remember all the altitudes and directions they'd take me relative to the compass and it was a bit too much to take on. It was on the edge of being too difficult than fun for me...
I do think the idea is really cool though and I think presenting it in a different, more player friendly way would work wonders on this game... Maybe particles nearby showing the wind direction, or some faint arrows in the sky that become more obvious the closer to get (just thinking out loud here) - but I feel it needs a little more help to the player to cross the bar of it being more fun than difficult would be great on this.
Also, I feel there should be a limit to how fast the balloon moves - currently, it can reach speeds that make me feel quite sick. I think the game will still be really playable if there was a much slower limit to the balloon and perhaps sub-targets to reach before landing on the land target directly.
Overall a really great idea with just a few practical issues getting in the way - a great job though!